By: Associated Press

Homes, trees and automobiles damaged by Monday's tornado are seen by early morning light in Moore, Okla., on Tuesday. Photo by Steve Sisney, The Oklahoman / NewsOK.com

President Obama declared a major disaster in Oklahoma Tuesday and has ordered federal aid to supplement state and local funds.

Emergency response teams are continuing to search in the rubble after the mile-wide twister destroyed homes and roads in Moore, Okla., outside of Oklahoma City. On Tuesday morning, the state medical examiner revised its death toll from the tornado to 24 people, including nine children. Authorities said initially that as many as 51 people were dead.

Federal Emergency Management Agency director Craig Fugate is due in Oklahoma City Tuesday to ensure federal resources are deployed properly. According to Presidential Spokesperson Jay Carney, FEMA has adequate funds for recovery efforts, but did not rule out the possibility of additional request for money from congress.

Homeland Security Secretary Janet Napolitano is scheduled to travel to the state Wednesday. The White House has not announced a presidential visit to the damaged areas, except to say that the president wants to make sure travel plans won't interfere with recovering efforts.

The National Weather Service announced Tuesday that the tornado was a top-of-the-scale EF-5 twister with winds of at least 200 mph. The Associated Press reported Tuesday that the agency upgraded the tornado from an EF-4 on the enhanced Fujita scale to an EF-5 based on what a damage assessment team saw on the ground. The tornado's path was 17 miles long and 1.3 miles wide.

By: Larisa Epatko

Photo of a Facebook user by Rodrigo Buendia/AFP/Getty Images.

Social networking websites such as Facebook and Twitter have helped users mobilize around a common cause like never before. But what if their message is one of hate?

The Simon Wiesenthal Center, a Los Angeles-based group working against global racism, has compiled a list of hundreds of websites it deems hateful and is pushing their host sites to remove them. They range from a white supremacist motorcycle group's blog, to the sale of a Nazi-era ring on eBay.

The group's associate dean, Rabbi Abraham Cooper, recently spoke at a briefing on Capitol Hill, where he described the group's efforts and what they're up against.

By: Larisa Epatko

NewsHour correspondent Betty Ann Bowser visited residents just returning to their homes after tornadoes swept through Oklahoma and Kansas in 1999.

In 1999, Genny and Bob McLane, both in their 80s, had just redecorated their three-bedroom home in Del City, Okla., when the tornado hit.

It was a massive storm system that plowed through Oklahoma, Kansas, Arkansas, Texas and Tennessee from May 3 through 6 of that year. Sixty-six tornadoes struck Oklahoma and Kansas alone.

The one that swept through the Oklahoma City suburbs of Del City and Moore, which suffered another tornado on Monday, packed winds of 318 mph, making it the strongest tornado ever recorded. By comparison, Monday's tornado had 200 mph winds.

Paths of the tornados in 1999 and 2013. Map by the National Weather Service, Norman, Okla., office. Click on image for a larger version.

The McLanes escaped the storm in a nearby shelter and then were taken in by neighbors. They returned to their home several days later to see what was left, and NewsHour correspondent Betty Ann Bowser accompanied them at the time.

By: Associated Press

WASHINGTON -- The man who led the Internal Revenue Service when it was giving extra scrutiny to tea party and other conservative groups seeking tax-exempt status told Congress on Tuesday that he knew little about what was happening while he was still commissioner.

Douglas Shulman, who vacated his position last November when his five-year term expired, told the Senate Finance Committee he didn't learn all the facts until he read last week's report by a Treasury inspector general confirming the targeting strategy.

In his first public remarks since the story broke, Shulman said: "I agree this is an issue that when someone spotted it, they should have brought it up the chain. And they didn't. I don't know why."

Shulman testified at Congress' second hearing on an episode that has largely consumed Washington since an IRS official acknowledged the targeting and apologized for it in remarks to a legal group on May 10. Shulman and the two officials who testified at Tuesday's three-and-a-half hour session -- the outgoing acting commissioner, Steven Miller, and J. Russell George, the Treasury Department inspector general who issued the report -- were all sworn in as witnesses, an unusual step for the Finance panel.

By: Associated Press

Apple Inc. CEO Tim Cook testifies on Capitol Hill to explain the company's tax strategy.

WASHINGTON -- A Senate panel says Apple Inc. is avoiding billions of dollars in U.S. taxes by shifting profits to foreign affiliates and is prepared to question the company's chief executive Tuesday about the "loopholes."

Apple CEO Tim Cook is expected to explain the company's tax strategy to the Senate Permanent Subcommittee on Investigations, which released a detailed report Monday on the company's practices.

The world's most valuable company says it complies with the laws and pays "an extraordinary amount" in U.S. taxes.

Sen. Carl Levin, D-Mich., the panel's chairman, says Apple's use of loopholes in the U.S. tax code is unique among multinational corporations.

"Apple is exploiting an absurdity," Levin said at the start of the hearing.

The tone of the hearing turned tense before the Apple executives were scheduled to appear, as Sen. Rand Paul, R-Ky., an anti-tax hawk who reflects tea party sentiment, insisted that the subcommittee apologize to Apple for unfair scapegoating.

"If anyone should be on trial here it should be Congress ... for creating a bizarre and byzantine tax code," said Paul. "If you want to assign blame, this committee needs to look in the mirror and see who created that mess."

By: Nick Corcodilos

Have you ever been skeptical of headhunter Nick Corcodilos' unconventional advice? One job seeker decided to put some Ask The Headhunter methods to the test and the results were extremely successful. Photo by Justin Sullivan/Getty Images.

Nick Corcodilos started headhunting in Silicon Valley in 1979, and has answered over 30,000 questions from the Ask The Headhunter community over the past decade.

In this special Making Sense edition of Ask The Headhunter, Nick shares insider advice and contrarian methods about winning and keeping the right job, on one condition: that you, dear Making Sense reader, send Nick your questions about your personal challenges with job hunting, interviewing, networking, resumes, job boards, or salary negotiations. No guarantees -- just a promise to do his best to offer useful advice.

Nick Corcodilos: Once in a while, I like to publish a success story from a reader. It helps people see that others are using the methods we discuss -- and that the approach works. Here's one that just came in.

Andy H.: I just wanted to tell you that I got a new job. Though I got this job by responding to a posting on LinkedIn, I used some of your methods during the process. (See "The Basics.")

By: Associated Press

Watch the Senate Finance Committee hearing to review criteria employed by the IRS to identify tax exemption applications for greater scrutiny. Former IRS Commissioner Douglas Shulman is scheduled to testify.

WASHINGTON -- A leading Senate Democrat says the Internal Revenue Service's targeting of conservative groups was intolerable, and he is promising to get to the bottom of how it happened.

Senate Finance Committee Chairman Max Baucus made his remark Tuesday as his panel began Congress' second hearing on the extra scrutiny the IRS gave tea party and other conservative groups seeking tax-exempt status.

The Montana Democrat says his committee will follow the facts wherever they lead.

Scheduled to testify to Congress for the first time was former IRS Commissioner Douglas Shulman, who headed the agency for most of the period when it was improperly focusing on the conservative groups.

We will live stream the hearing in the player above.

By: Terence Burlij and Christina Bellantoni

Flipped vehicles are piled up outside the heavily damaged Moore Medical Center after a powerful tornado ripped through the area on Monday in Moore, Oklahoma. Photo by Brett Deering/Getty Images

A massive tornado ravaged a suburb of Oklahoma City on Monday, leveling buildings, killing at least 51 people, and temporarily brushing aside a trio of brewing political storms that had been the focus of official Washington in recent weeks.

President Barack Obama will receive a briefing from senior members of the administration's response team prior to delivering a 10 a.m. ET statement on the Sooner State rescue and recovery efforts from the White House State Dining Room. (Mr. Obama's original schedule had a series of closed meetings, including one with people affected by immigration policy.)

Watch the president's remarks on the situation in Oklahoma here.

At the same time, a Senate Finance Committee hearing will get underway on Capitol Hill, where lawmakers will hear testimony from the ousted acting IRS commissioner and the former head of the agency who was in charge during the period agents were targeting conservative groups that had applied for tax-exempt status.

By: Associated Press

Television footage shows the massive funnel cloud that moved across the suburbs of Oklahoma City Monday.

Update 11:48 p.m. President Obama signed a disaster declaration for Oklahoma, minutes ago.

BREAKING: President Barack Obama declares major disaster in Oklahoma after devastating tornado

— The Associated Press (@AP) May 21, 2013

Update 11:28 p.m. | The following AP video shows survivors being pulled from the debris and loaded into waiting ambulances.

Update 11:03 p.m. | Oklahoma Governor Mary Fallin and city officials held a press conference earlier this evening. Fallin said that Oklahoma had received offers for resources from governors from other states across the nation, as well as from President Obama. She added that for now, downed power lines, blocked roadways, and overloaded telephone networks were hindering the emergency response.

The Associated Press has published a set of maps and graphics showing the path of destruction in Oklahoma, the latest information about the number of people killed or injured in the storm, and some background information on tornadoes.

Update 10:19 p.m. | Earlier today, the National Weather Service provided these details on the tornado:

Newcastle-Moore OKC Tornado was on the ground approx. 40 minutes. Tornado warning was in effect for 16 minutes before tornado developed.

— NWS Norman (@NWSNorman) May 20, 2013

Update 9:16 p.m. | AP has tweeted that the state medical examiner's office is now reporting 51 killed in the Oklahoma tornado, with children among the dead.

BREAKING: State medical examiner's office: 51 killed in Oklahoma tornado, with children among the dead -RJJ

— The Associated Press (@AP) May 21, 2013

Update 8:55 p.m. | There are at least 37 people reported killed. Authorities expected the death toll to rise as emergency crews moved deeper into the hardest-hit areas. At least 60 people were reported hurt, including more than a dozen children.

Update 7:02 p.m. | The Associated Press is following the story in Moore, Okla., where the twister touched down. Follow their updates via Twitter:

BREAKING: Several children pulled out of rubble alive at Plaza Towers Elementary School in Moore, Okla. -RJJ

— The Associated Press (@AP) May 20, 2013

Update 6:17 p.m. | The National Weather Service says the tornado that hit Moore had wind speeds up to 200 mph. The weather service's preliminary classification of Monday afternoon's tornado was an EF-4 on the enhanced Fujita scale.

Update 5:30 p.m. | Authorities also report that an elementary school in the area took a direct hit from the twister.

Gary Knight with the Oklahoma City Police Department says the school suffered "extensive damage."

Update 5:05 p.m. EDT | The Associated Press is reporting that a mile-wide tornado has ripped through suburban Oklahoma City Monday afternoon.

Video showed homes and buildings in Moore, Okla., were reduced to rubble, and vehicles littered roadways south and southwest of Oklahoma City.

More:

• Live updates from NPR member station KGOU in Oklahoma.

• Live updates from The Oklahoman, including a map of the twister's path and video from the scene.

• Follow the tweets from the National Weather Service in Norman, Okla.

By: Meena Ganesan and david coles

Photo illustration by PBS NewsHour created with Pic Stich

Yahoo, the languishing tech pioneer, officially unveiled its acquisition of social blogging platform Tumblr on Monday. The $1.1 billion purchase by Yahoo could mean a whole world of things for both of the Internet companies, as well as for Yahoo chief executive -- and former Google executive -- Marissa Mayer.

We spoke with Rebecca Lieb, a research analyst of digital advertising and media for the Altimeter Group and Steven Levy, a writer for Wired, about the deal and Yahoo's strategy behind it.

Where does Tumblr fit into the Yahoo strategy?

There are handful of things Yahoo wants from this buy, according Rebecca Lieb, a research analyst of digital advertising and media for the Altimeter Group. They want to vastly expand the Yahoo audience, Lieb told the PBS NewsHour. "Not just eyeballs, but expanding into a demographic, the millennials, the 20-somethings."

Yahoo was once a relevant Internet body, Lieb said:

It very badly needs to re-invent itself, to be, if not cool at least relevant again ... And Tumblr brings an elusive component of coolness. One of Mayer's big challenges is keeping it cool when it is owned by a less cool corporate entity.

Steven Levy, a writer for Wired, dubs Tumblr an "image-enhancer" for Yahoo. Tumblr provides Yahoo with a way to increase its content output by repurposing user-generated material, Levy said, adding that the site elevates a platform already loved by so many people. "The technological success for Tumblr, and now Yahoo, will be teasing content out of people for free."

What does the Tumblr experience say about the future role of mobile?

Lieb said that mobile is increasingly about imagery and cites Facebook's revamp and focus on images after its acquisition of the social photo sharing tool Instagram. "A picture is worth a thousand words," she said. "People don't type about their dinner. They upload photos." Yahoo's pick-up of Tumblr could mean even more change in the future of Yahoo's mobile strategy visually.

While Yahoo has seen significant plays on mobile, Lieb said the company, along with Facebook and Google, has yet to find the winning formula yet. "No one has won," she said. "The battle is just beginning."

Why was there negative reaction among Tumblr users?

"Tumblr has a very indie feel to it," said Levy of what some have called the "hipster blogging service."

The idea of a conglomerate led by a former Gooogler taking hold of that content, he added, could be disturbing. The social website revolt is a familiar tale. You can see some of those reactions here.

Levy also noted that pre-Melissa Mayer, the Web pioneer had a "miserable reputation of taking on new companies and doing nothing with them." (Note Yahoo's 2005 acquisitions of Flickr and del.icio.us.)

Is there any way to tell how difficult it will be for Yahoo to make money with Tumblr?

"The model Yahoo doesn't want you to look at is NewsCorp buying Myspace, and the model they want you to look at is Google buying YouTube," said Levy. The strategy there? "Google made the smart decision to not call YouTube Google Video."

On Yahoo's newfound relationship with Tumblr, Lieb's advice is to be hands-off and leave it alone. "If Yahoo goes in and makes radical changes, the audience will defect." But Yahoo can build Tumblr's advertising model, Lieb said. "At the same time, Tumblr will bring a new form of non-advertising," or native content marketing to Yahoo.

Content marketing is less alienating to the young millennial audience Yahoo is courting, signaled in this acquisition, said Lieb.

Are these tech sector deals still running ahead of their real value or are they starting to calm down?

While the jury's still out on the $1 billion Facebook-Instagram deal, YouTube surely helped Google, both Lieb and Levy agree. But these acquisitions are not the type that are expected to break even by the next quarter or even by the end of the next fiscal year, said Lieb.

"Generally these mergers don't work," said Levy, noting that for every Google success met by companies like Android and YouTube, there are ten other companies that acquired and had failures.

Watch Monday's NewsHour for more on the blockbuster merger.