PHILADELPHIA

An Amtrak train abruptly overturned in Philadelphia, killing at least five people and injuring dozens of others, some of whom had to scramble through the windows of toppled cars to escape. The accident has closed the nation’s busiest rail corridor between New York and Washington as federal investigators begin sifting through the mangled remains to determine what went wrong.

Train 188, a Northeast Regional, left Washington, D.C. and was headed to New York when it derailed shortly after 9 p.m. Tuesday. Amtrak said the train was carrying 238 passengers and five crew members.

More than 140 people went to hospitals to be evaluated or treated, and six were critically injured.

Amtrak said the cause of the derailment was not known and that it was investigating. It was bringing in lights to illuminate the scene overnight as workers examined the wreckage.

The National Transportation Safety Board said it was launching an investigative team, which would arrive at the site Wednesday morning. The Federal Railroad Administration said it was dispatching at least eight investigators to the scene.

The front of the train was going into a turn when it started to shake before coming to a sudden stop.

An Associated Press manager, Paul Cheung, was on the train and said he was watching Netflix when “the train started to decelerate, like someone had slammed the brake.”

Cheung said another passenger urged him to escape from the back of his car, which he did. He said he saw passengers trying to escape 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.”

One passenger, Daniel Wetrin, was among more than a dozen people taken to a nearby elementary school afterward.

“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.”

Police swarming around Tuesday’s derailment site, in Port Richmond, a workingclass area, told people to get back, away from the train. They pleaded with curious onlookers: “Do NOT go to scene of derailment. Please allow first responders room to work.”

Roads all around the crash site were blocked off. Hundreds of firefighters surrounded the train cars, taking people out.

Several injured people, including one man complaining of neck pain, were rolled away on stretchers. Others wobbled while walking away or were put on city buses. An elderly woman was given oxygen.

Former U.S. Rep. Patrick Murphy was on the train and said he helped people. He tweeted photos of firefighters helping other people in the wreckage.

Sen. Tom Carper of Delaware also was on the Amtrak train but got off in Wilmington, shortly before the derailment. He later tweeted that he was “grateful to be home safe and sound.”

The area where the derailment occurred is known as Frankford Junction and has a big curve. It’s not far from where one of the nation’s deadliest train accidents occurred: the 1943 derailment of The Congressional Limited, from Washington to New York, which killed 79 people.

Amtrak said rail service on the busy Northeast Corridor between New York and Philadelphia had been stopped. The mayor, citing the mangled train tracks and downed wires, said, “There’s no circumstance under which there would be any Amtrak service this week through Philadelphia.”

Gov. Tom Wolf, who was in touch with the mayor and other state and local officials about the derailment, thanked the first responders for “their brave and quick action.”

“My thoughts and prayers are with all of those impacted by tonight’s train derailment,” he said in a statement. “For those who lost their lives, those who were injured, and the families of all involved, this situation is devastating.”