Philadelphia's mayor said the train's data recorder has been recovered, but officials warned that the number of people unaccounted for was not yet confirmed after last night's crash and that search-and-rescue work was taking precedence over the investigation.
"It's a devastating scene," said Robert Sumwalt of the National Transportation Safety Board.
The rail corridor between New York and Washington remained closed as investigators looked for what went wrong. President Barack Obama called the derailment "a tragedy that touches us all."
Amid fears that the death toll could rise, Mayor Michael Nutter said some passengers listed on the Amtrak manifest might not have boarded the train, while others might not have checked in with authorities.
The mayor said some of the seven train cars, including the engine, "completely overturned, on their side, ripped apart." The train, traveling from Washington, D.C. To New York City, lurched to the side and flew off the tracks at a notorious curve not far from the scene of one of the nation's deadliest train wrecks more than 70 years ago.
