Federal investigators said on Wednesday that preliminary data showed an Amtrak train in Philadelphia was traveling at more than 100 miles per hour (160 kilometres per hour), or roughly twice the speed limit, when it derailed, killing seven people and injured more than 200.

The speed of the train was recorded in the so-called black box data recorders that were recovered from the wreckage, while emergency crews searched for more survivors and victims of the crash.

The recorders were taken to Amtrak's operations center in Delaware to download information like the train's speed, images from a video camera on the engine and a log of when the train's operator used tools like the brake, throttle and horn, officials said at a news conference.

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Passengers who emerged battered and bloodied described a chaotic, terrifying scene, with people thrown against walls, furniture and each other, and luggage and other loose items flying through the air and hitting people.

The accident occurred at a rail yard called Frankford Junction, northeast of downtown, where multiple freight and passenger routes converge, and Amtrak's Northeast Corridor makes one of its sharpest turns, requiring reduced speeds.

"It is an absolute disastrous mess," Mayor Michael A. Nutter of Philadelphia said of the scene. "Never seen anything like this in my life."

By midday, the names of the victims began to trickle out. The U.S. Naval Academy confirmed that one of its midshipmen was among the dead, and family members identified him as Justin Zemser of New York, a former student body president at Channel View High School.

"We're not ready to talk yet. We are just grieving, and when we are ready we will be in touch," said a relative, who did not want to be identified.

The Associated Press said that one of its employees, Jim Gaines, 48, a video software architect who lived in Plainsboro, New Jersey, was also killed.

Nutter said that the search of the twisted wreck for more people, living or dead, was "still in process," and that some passengers have not yet been found, but officials were still not sure how many were missing. "We have not completely matched the manifest that we received from Amtrak with the patient or hospital records," he said.

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Some people who congregated at Philadelphia's 30th Street Station said they had not been able to locate loved ones.

One of those unaccounted for, co-workers said, was Rachel Jacobs, chief executive officer of ApprenNet, an education technology company in Philadelphia. On Twitter, the company posted a message: "We are still looking for Rachel & hope she will be with her family soon."

Philadelphia's director of emergency management, Samantha Phillips, said, "Our hospitals treated over 200 patients last night and this morning."

The mayor said the engineer of the train "was injured to some extent" but has spoken to the Philadelphia police about what happened.

The New York-bound train jumped the tracks at about 9:30 p.m. Tuesday, tossing around the 238 passengers and five crew members, as most of the train's passenger cars tumbled onto their sides and crumpled. One car was particularly badly mangled, looking like nothing so much as a crushed and torn soda can.

Investigators from the National Transportation Safety Board began to arrive before 5 a.m., said Robert Sumwalt, a board member, adding that they may be able to release more information Wednesday afternoon. The FBI was also investigating.

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On Wednesday, a crane moved into position and began attempting to lift the damaged cars. The wreck severed Amtrak's Northeast Corridor, one of the nation's busiest rail routes, and the Southeast Pennsylvania Transportation Authority's commuter train line from Philadelphia to Trenton, stranding thousands of passengers and threatening to snarl travel for days or weeks to come.

Temple University Hospital received 54 patients from the wreck, including one who died overnight from a massive chest injury, Herbert E. Cushing, the chief medical officer, said Wednesday. He said that most of the patients suffered fractures from being thrown around the train, and that 25 remained in the hospital, including eight people in critical condition.

"There were lots of people from all around the world" among the injured, he said, including patients from Albania, India and Spain.

As officials worked to notify passengers' family members about their relatives, Nutter said most of them were not from the Philadelphia area, with more hailing from Washington, New York and New Jersey.

About 20 minutes before the crash, on the same line but a few miles away, "an unknown projectile" struck a SEPTA commuter train and damaged a window, an authority spokeswoman said. It was not clear whether the two incidents were related.

Amtrak officials said they were working to set up a family assistance center at a downtown hotel.

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"The guy next to me was unconscious, so I just kind of picked him up and slapped him in the face and said 'Hey buddy, get up, get up,' and he came to," said Patrick J. Murphy, a former congressman from Pennsylvania, who was on the train.

The engine pulling the train separated from the passenger cars, left the tracks, rumbled through a dirt area and came to rest diagonally across other sets of tracks.

After the crash, emergency workers carrying flashlights and ladders moved frantically from car to car helping passengers off the train, some bloodied, others dazed. Parts of the damaged cars were so badly mangled that firefighters had to use hydraulic tools to rescue people trapped inside.

"Train cars are overturned," said the Philadelphia fire commissioner, Derrick J. V. Sawyer. "They're in horrible shape. There's a bunch of debris down there, sharp objects. It's a dangerous situation for responders, even more dangerous for the riders out there."

The train had at least seven cars, including the engine, and six cars overturned. One car struck a steel utility pole, and a stretch of bent and twisted track could be seen near the wreckage, indicating the sheer force of the crash.

Amtrak identified the train as Northeast Regional Train 188, from Washington to New York. Remarkably, most people were able to walk away from the crash site.

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Injured passengers were taken from the scene in ambulances and on buses to hospitals. Aria Health, which has two hospitals nearby, said it had received 59 patients, including walk-ins. Maria Cerceo Slade, a spokeswoman, said most of the patients had minor injuries.

The cause of the crash was not known. It occurred close to Frankford Avenue and Wheatsheaf Lane, near a bend in the track. Nutter said it was too early to tell whether it had played a role in the crash or if there were other factors.

"We have no idea what kind of speed there we're talking about," Nutter said, or "what else happened out there."

He added, "And I'm not going to speculate on that."

Still, the derailment Tuesday took place in roughly the same area of track that was the site of one of the nation's deadliest rail accidents. On Labor Day in 1943, a 16-car Pennsylvania Railroad Congressional Limited train carrying military service members on leave derailed near the same curve, killing 79 people and injuring 117.

Officials concluded that a hot journal box had burned off and caused an axle to snap, which sent the train catapulting off the track.

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Amtrak trains on the Northeast Corridor are allowed to travel at speeds exceeding 100 mph. But conductors are required to proceed at reduced speeds in urban and residential areas, such as where the derailment occurred.

The Northeast Corridor, which runs between Boston and Washington, is one of the railroad's busiest and most profitable lines. But officials have long complained that the agency needs more subsidies from Congress to improve the railroad's deteriorating infrastructure and replace aging equipment.

The derailment prompted a large response from several federal, state and local agencies. More than 200 police officers and 120 firefighters went to the crash site, as did dozens of officials from the FBI, the Department of Homeland Security and other agencies.

An Amtrak spokesman said an emergency hotline, 800-523-9101, had been set up for relatives of anyone who may have been on the train.

Amtrak employees said that New Jersey Transit would honor Amtrak tickets to several nearby stations, including Trenton. Other passengers tried to find alternate routes home on regional bus services like Megabus and BoltBus.