JIM LEHRER: A new scare involving mail bombs erupted today in Greece. It happened just three days after bombs were intercepted in England and Dubai. Ray Suarez has the first of the day's two major stories.
RAY SUAREZ: The drama in Greece involved a parcel bomb addressed to the Mexican Embassy in Athens. It exploded at a delivery service, burning one employee.
Two men were arrested with more bombs, including one addressed to French President Nicolas Sarkozy. Police blamed an anarchist group that's been involved in previous plots. But the Athens attack came amid an international alert over bombs sent by air from Yemen to the U.S. and linked to al-Qaida.
On Friday, explosives addressed to synagogues around Chicago were pulled off planes in England and Dubai.
U.S. DEPUTY NATIONAL SECURITY ADVISOR JOHN BRENNAN: We can't presume that there are none other that are out there.
RAY SUAREZ: Deputy National Security Adviser John Brennan spoke Sunday, as he consulted with officials here and abroad.
JOHN BRENNAN: So, what we're trying to do right now is to work very closely with our partners overseas to identify all packages that left Yemen recently, and to see whether or not there are any other suspicious packages out there that might contain these IEDs.
RAY SUAREZ: The bombs involve desktop printers rigged with a powdered explosive and a cell phone circuit board for a detonator. Yemeni officials were hunting Ibrahim Hassan al-Asiri, the suspected bombmaker from Saudi Arabia. He's believed to be working with al-Qaida's Yemeni branch.
He's also been linked to the failed bombing attempt last Christmas on a plane arriving in Detroit. Security officials in Yemen said information about this latest plot came from Jabir al-Fayfi, an al-Qaida militant who surrendered to Saudi authorities last month.
In Sanaa today, crowds of supporters cheered a Yemeni student, Hanan al-Samawi, who was arrested over the weekend, then released. Investigators said she wasn't involved after all.
HANAN AL-SAMAWI, released suspect (through translator): I thank God and my family and colleagues and all the people who have supported me.
RAY SUAREZ: In the meantime, American agents were sent to Yemen to consult on airport and cargo security. And terror experts said it's clear air screening everywhere will need to be stepped up.
MICHAEL CHERTOFF, Former U.S. Homeland Security Secretary: I think they want to inflict damage, death and destruction on the United States. And we're going to have to now look for a whole wide range of tactics.
RAY SUAREZ: On the home front, the FBI urged caution about any packages arriving from overseas without return addresses or with excess postage.
In London, British Prime Minister David Cameron convened a crisis committee and Home Secretary Theresa May announced new measures.
THERESA MAY, British Home Secretary: We will update the guidance given to airport security personnel based on what we have learned to enable them to identify similar packages in future. From midnight tonight, we will extend the suspension of unaccompanied air freight to this country, not just from Yemen, but also Somalia.
RAY SUAREZ: Germany went further, banning not only cargo planes from Yemen, but passenger flights as well.