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.
The mayor said the train's engineer, whose name has not been released, was among the injured. The engineer was treated at a local hospital and later gave a statement to police, Nutter said. A Philadelphia police spokesman declined comment.
The wreck was the latest in a series of rail accidents on heavily travelled passenger train routes over the past year, raising new concerns about the state of the country's aging rail infrastructure and fresh calls for technology that could improve safety.
Positive train control (PTC) automatically slows or even halts trains that are moving too fast or heading into a danger zone. Under current law, the rail industry must adopt the technology by year-end.
But the crash came a day before the House Appropriations Committee approved a transportation budget for the next fiscal year that included a funding cut for Amtrak.
One amendment proposed by Democrats called for $825 million (S$1093 million) in capital investments in PTC technologies for passenger rail, but it was blocked by the Republican majority.
"LIKE A SECOND FAMILY"
Vice President Joe Biden, who often took Amtrak to Washington when he was a senator living in Delaware, expressed shock and sorrow.
"Amtrak is like a second family to me, as it is for so many other passengers," said Biden, who has estimated taking some 8,000 Amtrak trips to and from Washington during his career.
One of the people killed was Midshipman Justin Zemser on leave from the US Naval Academy in Annapolis, Maryland, an academy spokesman said.
An Associated Press video software architect was also among those killed. Jim Gaines, a 48-year-old father of two, had attended meetings in Washington and was returning to his home in Plainsboro, New Jersey, when the train derailed Tuesday night. His death was confirmed by his wife, Jacqueline.
In March, 21 people were injured in Los Angeles, when a commuter train collided with a car. A month earlier, 50 people were hurt and an engineer fatally injured when a Los Angeles-bound Metrolink train struck a pickup truck.
Also in February, six people were killed and a dozen injured when a commuter train hit a car stalled on the tracks north of New York City. The driver of the vehicle also died.
The train derailed in the city's Port Richmond neighborhood along the Delaware River, near the site of a 1943 rail accident that killed 79 people and injured 117 others, according to the National Railway Historical Society.
Tuesday's derailment left travelers along the Washington-to-New York corridor scrambling to find alternatives.
At New York's LaGuardia Airport, attorney Wayne Hess said he had planned to take the train back to Washington but instead booked a flight after hearing of the accident.
"It made me feel lucky because I came up yesterday," Hess said.