Despite pressure from Congress and safety regulators, Amtrak had not installed along that section of track Positive Train Control, a technology that prevents trains from going faster than the speed limit, the railroad agency said.
    The engineer's name was not immediately released.
    The accident closed the nation's busiest rail corridor between New York and Washington — snarling the morning commute and forcing thousands of travelers to find some other way to reach their destination — as investigators examined the wreckage and the tracks and gathered up other evidence.
    The dead included an AP employee and a midshipman at the U.S. Naval Academy.
    Nutter said some people remained unaccounted for, though he 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," Nutter said in the afternoon. He said rescuers expanded the search area and used dogs to look for victims in case someone was thrown from the wreckage.
    The train was en route from Washington to New York with 238 passengers and five crew members listed aboard. The notoriously tight curve is not far from the scene of one of the nation's deadliest train wrecks more than 70 years ago.
    Passengers scrambled through the windows of toppled cars to escape. One of the seven cars was severely mangled. Hospitals treated more than 200 people for injuries that included burns and broken bones. At least 10 remained hospitalized in critical condition.
    Amtrak inspected the stretch of track on Tuesday, just hours before the accident, and found no defects, according to the Federal Railroad Administration. In addition to the data recorder, the train had a video camera in its front end that could yield clues to what happened, said NTSB member Robert Sumwalt.
    Passenger Jillian Jorgensen, 27, was seated in the quiet car — 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.
    The train derailed, 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 to the AP. "The scene in the car I was in was total disarray, and people were clearly in a great deal of pain."
    Award-winning AP video software architect Jim Gaines, a 48-year-old father of two, was among the dead. Also killed was Justin Zemser, a 20-year-old Naval Academy midshipman from New York City.
    An AP manager, Paul Cheung, was on the train and said he was watching a video on his laptop when "the train started to decelerate, like someone had slammed the brake."
    "Then suddenly you could see everything starting to shake," he said. "You could see people's stuff flying over me."
    Cheung said another passenger urged him to escape from the back of his car, which he did. He said he saw passengers trying to get out through the windows of cars tipped on their sides.
    "The front of the train is really mangled," he said. "It's a complete wreck. The whole thing is like a pile of metal."
    Another passenger, Daniel Wetrin, was among more than a dozen people taken to a nearby elementary school.
    "I think the fact that I walked off kind of made it even more surreal because a lot of people didn't walk off," he said. "I walked off as if, like, I was in a movie. There were people standing around, people with bloody faces. There were people, chairs, tables mangled about in the compartment ... power cables all buckled down as you stepped off the train."
    Several people, including one man complaining of neck pain, were rolled away on stretchers. Others wobbled as they walked away or were put on buses. An elderly woman was given oxygen.
    The area where the wreck happened is known as Frankford Junction, situated in a neighborhood of warehouses, industrial buildings and homes.
    It is not far from the site of the 1943 derailment of the Congressional Limited, from Washington to New York, which killed 79 people.
    Amtrak carries 11.6 million passengers a year along its busy Northeast Corridor, which runs between Washington and Boston.
    The mayor, citing the mangled tracks and downed wires, said: "There's no circumstance under which there would be any Amtrak service this week through Philadelphia."