Amtrak train was traveling at more than 100 mph before crash that killed 7

The Amtrak train that derailed near Philadelphia Tuesday night -- killing at least seven and sending more than 200 to area hospitals -- appeared to have been traveling at more than 100 mph, according to preliminary data collected by the National Transportation Safety Board.

Two people with knowledge of the investigation told the Wall Street Journal that the train was going twice the speed limit in the section as it approached a sharp curve on the track.

The Associated Press analyzed surveillance video of the train just before the crash and estimates that the train was moving at 107 mph.

Authorities recovered the black box from the train and are inspecting video footage recorded from the front of the train moments before the accident.

Crews at the scene in the residential area of Port Richmond are still focused on search and rescue since there are a number of passengers still unaccounted for, but the NTSB is alongside conducting an investigation and collecting perishable evidence at the site.

Robert Sumwalt, a board member for the NTSB, said a multidisciplinary team is at the scene that will study the track, train signals, operation of the train and the condition of the train.

He said the train's recorders, which were sent to Delaware for analysis, can provide investigators with views from a forward-facing camera and elements like the speed of the train or if the brakes were engaged at any point. The conductor, who received medical treatment, will make a statement to the Philadelphia Police Department, Mayor Michael Nutter said at a Wednesday press conference.

Philadelphia Police commissioner Charles Ramsey told the Philadelphia Inquirer the train's engineer did not offer a statement at a Wednesday afternoon meeting with authorities and had an attorney present when he left the detective office.

Sumwalt called the black boxes 'key' to the investigation

The names of the victims were not immediately released. A Pentagon official told Fox News that a U.S. Naval Academy midshipman was one of those killed. On Tuesday afternoon, crews announced that they pulled another body from the wreckage.

As many as six more people remain critically injured. Amtrak and city authorities estimated that 238 passengers and five Amtrak employees were on the Northeast Regional Train 188, traveling from Washington, D.C., to New York City, when it went off the rails at about 9:30 p.m. local time. As the train neared a curve in a residential area of Port Richmond, it suddenly slowed, according to one witness.

"The train started to decelerate, like someone had slammed the brake," Paul Cheung, an Associated Press employee who was watching a movie on Netflix when disaster struck, said. "Then suddenly you could see everything starting to shake. 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."

The chilling audio from Fire Radio calls following the derailment captured the moments that first responders arrived on scene and assessed the immediate situation, MyFoxPhilly.com reported.

"Notify Amtrak to shut down the entire NE corridor. We have a major event here. We have people on the tracks, and a couple of cars overturned," the caller said. "We are going to classify this as a mass casualty incident."

Philadelphia Mayor Michael Nutter told reporters early Wednesday that not all of the passengers on the train's manifest had been accounted for.

"It is an absolute, disastrous mess," Nutter said. "Never seen anything like this in my life."

The mayor added that there were train cars that were "completely overturned, on their side, ripped apart."

"It is a devastating scene down there," he said. "We walked the entire length of the train area, and the engine completely separated from the rest of the train, and one of the cars is perpendicular to the rest of the cars. It's unbelievable."

Amtrak released a statement early Wednesday saying it was "deeply saddened by the loss of life." The company earlier announced that service between New York and Philadelphia had been suspended indefinitely.

PHOTOS FROM INSIDE THE DEADLY TRAIN DERAILMENT

Nutter, citing the mangled train tracks and downed wires, said, "There's no circumstance under which there would be any Amtrak service this week through Philadelphia."

Passenger Beth Davidz, who had boarded the train minutes earlier at Philadelphia's 30th Street Station, told Fox News' Megyn Kelly that the train was approximately 10 minutes out from the station when it went into a "slow slide."

"People were helping each other to get up, helping the people who were trapped," Davidz said. "We weren't quite sure how to get out of the car."

Another passenger, Daniel Wetrin, was among more than a dozen people taken to an 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."

Late Tuesday night, rescue workers used the jaws of life to free passengers trapped in the most badly damaged cars, while emergency workers with flashlights and ladders were going through the wreckage helping dazed and injured passengers off the train. As dawn broke, investigators from the National Transportation Safety Board arrived to begin a probe that could take weeks. Amtrak also said it was investigating the crash and trucked in portable lights to illuminate the scene overnight as workers examined the wreckage.

The area where the derailment occurred is known as Frankford Junction and has a big curve in the tracks. 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.

Roads around the area were blocked off as police swarming around the crash site told people to get back. They pleaded with curious onlookers: "Do NOT go to scene of derailment. Please allow first responders room to work."

The Philadelphia Inquirer reported, citing a fire official, that two people were found under the train when first responders arrived. 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 Pennsylvania Congressman Patrick Murphy was on the train and said he had been helping people. He tweeted several photos of firefighters helping people in the wreckage.