Joseph Kaczmarek/AP

Officials Investigate Cause of Deadly Train Accident Outside Philadelphia

A New York-bound Northeast Regional train derailed Tuesday night, killing at least six and injuring more than 50.

At least six people have been killed and dozens are injured after an Amtrak train traveling from Washington to New York City derailed in Philadelphia on Tuesday night.

Philadelphia Mayor Michael Nutter confirmed the first five deaths during a press conference Tuesday night. He said he has "never seen anything like this in my life." Temple University Hospital confirmed the sixth death Wednesday morning, saying the passenger died of a "massive chest injury."

Speaking to reporters just before 7 a.m. Wednesday, Temple's chief medical officer Herbert Cushing noted that 25 patients were treated and released at his hospital, and 25 are still in hospital care. Cushing said eight patients remain in critical condition. The passengers, Cushing said, included several people from other countries who had been travelling in the U.S.

The Northeast Regional Train 188 departed Union Station at 7:15 p.m., according to Amtrak's train status tracking. The train derailed just after 9 p.m.  There were 238 passengers and five crew members on board, according to Amtrak.

AP reports more than 140 passengers went to hospitals.

As of Wednesday morning, the cause of the derailment is still unknown. A law enforcement source told ABC's Philadelphia affiliate that a black box has been recovered from the train and will be analyzed in Delaware. The train's speed is currently the focus of the investigation. The FBI has also dispatched agents to the crash site.

Amtrak directed people with questions about friends and family aboard the train to call 800-523-9101 for information.

Amtrak said early Wednesday morning that there will be no service between New York and Philadelphia Wednesday.

Former Rep. Patrick Murphy was on Train 188, and tweeted a photo of what he saw.

Paul Cheung, an Associated Press employee who was on Train 188, told the AP that the front of the train was "really mangled."

"It's a complete wreck," he said. "The whole thing is like a pile of metal." NBC's Philadelphia affiliate showed footage of the wreckage:

The train's seven cars were all impacted, AP reports, and some cars were "completely overturned, on their side, ripped apart." Six cars overturned and one hit a steel utility pole, according to The New York Times.

First responders were on the scene removing injured passengers and loading them into ambulances.

Sen. Thomas Carper of Delaware said in a statement Tuesday night that he was on Train 188 and got off at Wilmington. "I am grateful to be home safe and sound in Wilmington, and my heart goes out to all those on the train tonight," he said. "I hope all of those that are injured recover quickly, and I will keep them in my thoughts and prayers."

Sen. Bob Menendez, D-N.J, also detailed a personal connection to the crash in a Wednesday statement. "This hits especially close to home. There was a period of time last night when I didn't know the whereabouts of my son, who was scheduled to be on an Amtrak back to New Jersey, and later found out he was on the next train and safe," he said. Unfortunately, many New Jersey families this morning aren't as fortunate as they search for loved ones and answers." Menendez said he's been in touch with Transportation Secretary Anthony Foxx.

The National Transportation Safety Board said Tuesday night that it has dispatched a team to investigate the crash which would arrive Wednesday morning, when they plan hold a press conference.

Another Amtrak train was involved in a crash on Sunday. The train, carrying 163 passengers, struck a car on the tracks on its way from Washington to New Orleans, killing the driver of the vehicle. The location of Tuesday's crash was the site of a major train accident in 1943.

Amtrak accounts for 77 percent of air and rail travel between Washington and New York, and overall ridership has spiked in recent years. Still, the company has been running a deficit every year for decades. Back in Washington, the House Appropriations Committee is scheduled to mark up a $55 billion transportation spending bill on Wednesday that would provide $289 million in federal funding for Amtrak.

Speaking on CNN Wednesday morning, White House Press Secretary Josh Earnest said "if there is an opportunity for us to make further investments in our infrastructure that would better safeguard the travelling public, than those are investments that we should make, both because of the improvements on safety but also because of the positive economic benefit it would have in terms of creating jobs and stimulating economic growth all across the country."

This story, originally published Tuesday night, has been updated with more information Wednesday.