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.

Mayor Michael Nutter, who confirmed the deaths, said the scene was horrific and not all the people on the train had been accounted for.

“It is an absolute disastrous mess,” he said. “I’ve never seen anything like this in my life.”

He said all seven train cars, including the engine, were in “various stages of disarray.” He said there were cars that were “completely overturned, on their side, ripped apart.”