Philadelphia - An Amtrak passenger train headed to New York City derailed and crashed in Philadelphia on Tuesday night, and several people appeared to be injured.Train 188, a Northeast Regional, had left Washington, DC, earlier on Tuesday. The front of the train was going into a turn when it shook.An Associated Press employee, Paul Cheung, was on the train and said it appeared it went off the tracks. He said he was fortunate to be at the back of the train and the front of it "looks pretty bad." He said he saw "some people mangled up."Police swarming around the crash site, in Port Richmond, a working-class area, told people to get back, away from the train. They pleaded with curious onlookers: "Do not go to scene of derailment. Please allow 1st responders room to work."Roads all around the crash site were blocked off.Several injured people, including one man complaining of neck pain, were rolled away on stretchers. Others wobbled while walking away. 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 people in the wreckage."Pray for those injured," he said.Cause unknownThe cause of the crash was unknown. Amtrak said it was aware of the derailment and would provide updates later. The National Transportation Safety Board said on Tuesday night it was gathering information about the derailment.Another Amtrak train crashed on Sunday. That train, bound for New Orleans, struck a flatbed truck at a railway crossing in Amite, killing the truck's driver and injuring two people on the train.In March, at least 55 people were injured when an Amtrak train collided with a tractor-trailer that was stuck on the tracks in North Carolina.Port Richmond, the site of Tuesday's crash, is one of five neighbourhoods in what's known as Philadelphia's River Wards, dense rowhouse neighbourhoods located off the Delaware River.