Daylight on Wednesday revealed the destruction and devastation caused by an Amtrak train derailment in Philadelphia that left at least six people dead and injured dozens more, several critically, as survivors recalled a terrifying wreck that plunged them into darkness and chaos

Some passengers had to scramble through the windows of toppled cars to escape. One of the seven cars was completely mangled.

The accident closed the nation's busiest rail corridor between New York and Washington as federal investigators begin sifting through the twisted 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.

"It is an absolute disastrous mess," Mayor Michael Nutter said. "I've never seen anything like this in my life."

Nutter confirmed five deaths and said not all the people on the train had been accounted for. Temple University Hospital's Dr. Herbert Cushing said Wednesday a person died there overnight from a chest injury

More than 140 people went to hospitals to be evaluated or treated for injuries that included burns and fractures.

Amtrak said the cause of the derailment was not known and that it was investigating. The National Transportation Safety Board and the Federal Railroad Administration were also dispatching investigators to the site.