Investigators are back at the scene of yesterday's explosion at Yale University's law school. They are trying to determine exactly what caused the blast and how explosives got into the unoccupied room.
No one was injured, but the blast knocked down a partition between the classroom and an alumni lounge and sent smoke through the law school. One student says he was standing in a hallway when he saw "a huge fireball."
The law school will be closed today and tomorrow. Officials also say they will probably move a law school graduation ceremony scheduled for Monday to another location.