GWEN IFILL: Now to this weekend's deadly train accident in Canada, which claimed the lives of 13 people. More than 35 remain missing.
And we turn again to Hari for that story.
HARI SREENIVASAN: Disaster struck in the dark early Saturday. French Canadians looked on in the first frantic moments. And then at least five oil tanker cars exploded, and a fireball burst into the night sky.
Orange flames engulfed the core of Lac-Megantic, a Quebec town of some 6,000 people about 150 miles east of Montreal and near the Maine border. Railway officials said the parked train had gotten loose and hurtled downhill nearly seven miles before jumping the tracks.
WOMAN: You could see the train, but it was going so fast you couldn't even see between the cars, and then I saw a car lift up.
MAN: There was a ruckus. It leaped. There were big balls of fire above the cafe. And just in the time it took to cross the street, the street was filled with fire. It was a river of fire.
HARI SREENIVASAN: The raging fire and heavy black smoke forced a third of the town's residents from their homes. On Sunday, Canadian Prime Minister Stephen Harper toured the devastation, and said at least 30 buildings were destroyed.
PRIME MINISTER STEPHEN HARPER, Canada: At this point, the mood is quite good. The solidarity of everybody is quite strong, but I know there is going to be waves of emotion over the next few weeks, as the extent of this -- and this is a very big disaster in human terms -- as the extent of this becomes -- becomes increasingly obvious.
HARI SREENIVASAN: By today, search teams were still being hampered by the need to keep two more derailed tank cars from exploding. It was the fourth train accident involving oil shipments this year in Canada, and it raised new questions about the safety of transporting oil by railroad, all of this as the Obama administration weighs approval of the Keystone XL pipeline to move crude from Canada to U.S. refineries on the Gulf Coast.