More than 200 people have been treated at local hospitals. However, some people are still unaccounted for.
"It's a devastating scene. There are many first responders out there. They are working. They are examining the equipment, seeing if there are any more people in the rail cars," Robert Sumwalt of the National Transportation Safety Board said.
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.
A midshipman at the Naval Academy has been identified as one of the passengers who lost their life in the crash. ABC News said the victim's mother has identified him as 20-year-old Justin Zemser of Rockaway Beach, New York. The Naval Academy says Zesmer was on leave and en route to his home.
Award-winning AP video software architect Jim Gaines was also among those killed. Gaines, a 48-year-old father of two who joined the news agency in 1998, had attended meetings in Washington and was returning home to Plainsboro, New Jersey.
Mayor Michael Nutter said, "We will do everything we can to account for everyone who was on that train."
The mayor also cautioned that some passengers listed on the Amtrak manifest might not have boarded the train, while others might not have checked in with authorities.
The city is urging people who were on the train to call Amtrak and report in at 1-800-523-9101.
NTSB investigators arrived at the crash site around 4:00 a.m. Wednesday to begin their investigation.
The train's black box has been recovered and has been sent to the Amtrak Operations Center in Delaware for analysis.
The NTSB confirmed Wednesday afternoon preliminary data that shows the train speed exceeded 100 mph prior to the derailment.
Furthermore, an analysis by The Associated Press of surveillance video just before the deadly crash indicates it was traveling about 107 miles per hour as it approached a curve where the speed limit was 50 miles per hour.
Sources say the engineer of the Amtrak train was injured in the crash, and later questioned by investigators at the hospital.
Upon his release from the hospital the 32-year-old engineer spent hours inside East Detective headquarters, and according to Police Commissioner Charles Ramsey he declined to give a formal statement about the wreck, even after his union lawyer arrived.
Amtrak inspected the stretch of track on Tuesday, just hours before the accident, and found no defects, according to the Federal Railroad Administration.
There is hope that a forward facing camera at the front of the engine will provide some light into what happened.
Seven people are now confirmed dead, and 11 people are in critical condition and dozens of others were injured.
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.
In a statement, President Barack Obama said the derailment "is a tragedy that touches us all."
The president says he and the first lady were "shocked and deeply saddened" to hear of the derailment, and that he is offering prayers to the families who lost loved ones and the passengers beginning to recover.
Family members are searching for a number of passengers who remain unaccounted for.
Among the missing is Rachel Jacobs, the newly-hired CEO of a Philadelphia-based tech startup company. A friend tells Action News that Jacobs was on the train when it derailed.
Mayor Nutter says investigators have not yet matched the passenger manifest with hospital records, so there are a number of people still unaccounted for.
Overnight cranes and other heavy equipment were brought to the scene to begin moving the derailed cars.
At a press conference Tuesday night Mayor Michael Nutter said the scene was horrific.
"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."
"It is a devastating scene down there," Nutter said. "We walked the entire length of the train area, and the engine is completely separated from the rest of the train, and one of the cars is perpendicular to the rest of the cars. It's unbelievable."
Fire Commissioner Derrick Sawyer called it a level 3 mass casualty incident.
"I've never seen anything so devastating. They are in pretty bad shape. They have completely derailed from the track," Sawyer said.
Passenger Jillian Jorgensen, 27, was seated in the quiet car - the second passenger car - and said the train was going "fast enough for me to be worried" when it began to lurch to the right.
The train derailed, the lights went out and Jorgensen was thrown from her seat. She said she "flew across the train" and landed under some seats that had apparently broken loose from the floor.
Jorgensen, a reporter for The New York Observer who lives in Jersey City, New Jersey, said she wriggled free as fellow passengers screamed. She saw one man lying still, his face covered in blood, and a woman with a broken leg.
She climbed out an emergency exit window, and a firefighter helped her down a ladder to safety.
"It was terrifying and awful, and as it was happening it just did not feel like the kind of thing you could walk away from, so I feel very lucky," Jorgensen said in an email to the AP. "The scene in the car I was in was total disarray, and people were clearly in a great deal of pain."
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."
"Then suddenly you could see everything starting to shake," he said. "You could see people's stuff flying over me."
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 side.
"The front of the train is really mangled," he said. "It's a complete wreck. The whole thing is like a pile of metal."
Another passenger, Daniel Wetrin, was among more than a dozen people taken to a nearby elementary school afterward.
"I think the fact that I walked off (the train) kind of made it even more surreal because a lot of people didn't walk off," he said. "I walked off as if, like, I was in a movie. 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."
"Basically the train tilted over and rolled," one passenger told Action News.
The area where the derailment occurred near Frankford Avenue and Wheatsheaf Lane 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.
Police swarming around Tuesday's derailment 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. Waves of firefighters continuing toward 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.
"It was obviously a lot of mayhem People were pretty banged up, a lot of blood, a lot of bleeding," Murphy told Action News.
Local music producer Yameen was also aboard the train and recorded a rescue in progress.
Area resident David Hernandez, whose home is close to the tracks, heard the derailment.
"It sounded like a bunch of shopping carts crashing into each other," he said.
The crashing sound lasted a few seconds, he said, and then there was chaos and screaming.
Gov. Tom Wolf, who ordered all state flags to be lowered to half-mast, 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."
SEPTA says a number of its route will be affected due to the derailment. The latest information can be found on SEPTA.org.
The Associated Press contributed to this report.