Federal investigators have determined that an Amtrak train that crashed in Philadelphia, killing at least seven people, was careening through the city at 106 mph before it ran off the rails along a sharp curve where the speed limit drops to just 50 mph, yet they still don't know why it was going so fast.

Robert Sumwalt, of the National Transportation Safety Board, said a data recorder and a video camera in the train's front end could yield clues to what happened. Amtrak inspected the stretch of track on Tuesday, just hours before the accident, and found no defects, according to the Federal Railroad Administration.

Sumwalt said the engineer applied the emergency brakes moments before the crash but slowed the train to only 102 mph by the time the locomotive's black box stopped recording data. The speed limit just before the bend is 80 mph, he said.

The attorney for the engineer at the controls of an Amtrak train that careened off the tracks while traveling at an excessive speed said Thursday his client has no recollection of the accident.

Appearing on ABC's "Good Morning America", lawyer Robert Goggin said the engineer, Brandon Bostian, 32, of New York, suffered a concussion in Tuesday night's crash and had 15 staples in his head.

"He remembers coming into curve. He remembers attempting to reduce seed and thereafter he was knocked out," Goggin said.

The lawyer said the last thing the engineer remembered was coming to, looking for his bag, retrieving his cellphone and calling 911 for help.

Googin said his client was distraught when he learned of the devastation and believes the engineer's memory will likely return once the head injury subsides.

The engineer refused to give a statement to law enforcement and left a police precinct with a lawyer, police said. Sumwalt said federal accident investigators want to talk to him but will give him a day or two to recover from the shock of the accident.

Mayor Michael Nutter said he was frustrated to learn how fast the train was going. "Part of the focus has to be, what was the engineer doing?" Nutter said. "Why are you traveling at that rate of speed?"

More than 200 people aboard the Washington-to-New York train were injured in the wreck, which happened in a decayed industrial neighborhood not far from the Delaware River just before 9:30 p.m. Tuesday. Passengers crawled out the windows of the torn and toppled rail cars in the darkness and emerged dazed and bloody, many of them with broken bones and burns. At least 10 people remained hospitalized in critical condition on Wednesday.

It was the nation's deadliest train accident in nearly seven years. There is no Amtrak service between Washington and New York again on Thursday.

The NTSB finding about the train's speed corroborated an AP analysis done earlier in the day of surveillance video from a spot along the tracks. The AP concluded from the footage that the train was speeding at approximately 107 mph moments before it entered the curve.

Despite pressure from Congress and safety regulators, Amtrak had not installed along that section of track Positive Train Control, a technology that uses GPS, wireless radio and computers to prevent trains from going over the speed limit. Most of Amtrak's Northeast Corridor is equipped with Positive Train Control.

"Based on what we know right now, we feel that had such a system been installed in this section of track, this accident would not have occurred," Sumwalt said.

The notoriously tight curve is not far from the site of one of the deadliest train wrecks in U.S. history: the 1943 derailment of the Congressional Limited, bound from Washington to New York. Seventy-nine people were killed.

The dead in Tuesday's crash included an Associated Press employee, a midshipman at the U.S. Naval Academy, a Wells Fargo executive, a college administrator and the CEO of an educational startup.

Nutter said some people were unaccounted for but cautioned that some passengers listed on the Amtrak manifest might not have boarded the train, while others might not have checked in with authorities.

"We will not cease our efforts until we go through every vehicle," the mayor said.

The crash took place about 10 minutes after the train pulled out of Philadelphia's 30th Street Station with 238 passengers and five crew members listed aboard. The locomotive and all seven passenger cars hurtled off the track as the train made a left turn, Sumwalt said.

Of the engineer, Sumwalt said: "This person has gone through a very traumatic event, and we want to give him an opportunity to convalesce for a day or so before we interview him. But that is certainly a high priority for us, to interview the train crew."

Jillian Jorgensen was seated in the second passenger car and said the train was going "fast enough for me to be worried" when it began to lurch to the right. Then the lights went out, and Jorgensen was thrown from her seat.

She said she "flew across the train" and landed under some seats that had apparently broken loose from the floor.

Jorgensen, a reporter for The New York Observer who lives in Jersey City, New Jersey, said she wriggled free as fellow passengers screamed. She saw one man lying still, his face covered in blood, and a woman with a broken leg.

She climbed out an emergency exit window, and a firefighter helped her down a ladder to safety.

"It was terrifying and awful, and as it was happening it just did not feel like the kind of thing you could walk away from, so I feel very lucky," Jorgensen said in an email.

Among the dead were award-winning AP video software architect Jim Gaines, a father of two; Justin Zemser, a Naval Academy midshipman from New York City; Abid Gilani, a senior vice president in Wells Fargo's commercial real estate division in New York; Derrick Griffith, dean of student affairs and enrollment management at Medgar Evers College in Brooklyn, New York; and Rachel Jacobs, who was commuting home to New York from her new job as CEO of the Philadelphia educational software startup ApprenNet.

"It's incredible that so many people walked away from that scene last night," the mayor said. "I saw people on this street behind us walking off of that train. I don't know how that happened, but for the grace of God."

The area where the wreck happened is known as Frankford Junction, situated in a neighborhood of warehouses, industrial buildings and homes.

Amtrak carries 11.6 million passengers a year along its busy Northeast Corridor, which runs between Washington and Boston.

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Associated Press reporters Maryclaire Dale, Michael R. Sisak and Josh Cornfield in Philadelphia and Jack Gillum, Ted Bridis and Joan Lowy in Washington contributed to this story.