PHILADELPHIA - Federal investigators said on Wednesday that preliminary data showed an Amtrak train in Philadelphia was traveling at more than 100 miles per hour, or roughly twice the speed limit, when it derailed, killing seven people and injuring more than 200.
The National Transportation Safety Board's (NTSB) disclosure came as investigators pored over video footage and data from the black box aboard the train that crashed late Tuesday.
In addition to speed, the NTSB has said it was focusing on the condition of the tracks and equipment, crew training and the performance of the five-person crew.
The commuter rail route where the Amtrak train left the track was not governed by an advanced safety technology meant to prevent high-speed derailments, officials familiar with the investigation said.
Passenger rail service along Amtrak's Northeast Corridor, the country's busiest with 12 million passengers a year, was shut down immediately after the accident at about 9:30 p.m. EDT Tuesday (0130 GMT Wednesday), leaving travelers scrambling for alternatives.
The derailment also snarled commuter rail services that share Amtrak tracks in the Philadelphia area and beyond.
Nearly a day after Amtrak No. 188 jumped the track, rescue workers were still pulling apart the twisted metal and sifting through other debris left by the crash.
One of the seven cars landed upside down and three were tossed on their sides, while passengers and luggage were sent flying, survivors said, inflicting severe injuries on some of them.
Philadelphia Mayor Michael Nutter said at a news conference that seven people were confirmed dead, but authorities had not yet accounted for everyone believed to have been on board.
He said rescue teams expanded the search area out of fear that some victims may have been thrown from the train when it derailed.
"What we have to do today is make sure we're searching every car, every inch, every thousands of square feet to find or locate individuals who may have been on that train," Nutter said.
Eight people remained in critical condition at Temple University Hospital, one of several medical centres where the injured were taken, said Dr. Herbert Cushing, its chief medical officer.
All told, hospitals in the area reported treating more than 200 people, city officials said, out of 243 people, including the crew, who were believed on the train when it crashed. Officials are still trying to confirm the number on board.