Emergency personnel search through the wreckage of an Amtrak train that derailed Tuesday night in Philadelphia, killing at least five people who were on board. Joseph Kaczmarek/AP hide caption

itoggle caption Joseph Kaczmarek/AP

A fireball goes up at the site of an oil train derailment in Casselton, N.D., in this Dec. 30 photo. The fiery crash left an ominous cloud over the town and led some residents to evacuate. Bruce Crummy/AP hide caption

itoggle caption Bruce Crummy/AP

A fire burns west of Casselton, N.D., Monday, after oil tanker cars exploded following a train derailment. No one has been reported hurt in the derailment or fire. But officials are recommending residents of the town to stay away from the potentially toxic smoke. Ken Pawluk/AP hide caption

itoggle caption Ken Pawluk/AP