The investigation into why an Amtrak Northeast Regional train derailed outside Philadelphia late Tuesday, killing at least seven and injuring over 200 others, has focused on the actions of the train's engineer after it was revealed that the train was traveling at more than twice the legal speed limit seconds before the crash. 

WTXF reported that the engineer on Northeast Regional Train 188 has been identified as 32-year-old Brandon Bostian. Police sources told the station that Bostian was taken to a local hospital after the crash and blood samples were taken from him in accordance with standard procedure. The sources also said that Bostian asked for a lawyer and told city investigators he didn't remember what happened.

NTSB board member Robert Sumwalt told reporters earlier Wednesday that the train was traveling at 106 mph as it entered a sharp curve at Frankford Junction where the speed limit was 50 mph. The engineer he said, launched a "full emergency brake application"  a few seconds before the train derailed 11 minutes after leaving the Philadelphia station, crumpling cars and throwing around many of the 243 aboard.

Sumwalt said federal accident investigators want to talk to Bostian but will give him a day or two to recover from the shock of the accident.

"This person has gone through a very traumatic event, and we want to give him an opportunity to convalesce for a day or so before we interview him," Sumwalt said. "But that is certainly a high priority for us, to interview the train crew."

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Philadelphia District Attorney Seth Williams told WTXF Wednesday that it was too early to determine whether to pursue a criminal investigation, explaining that many details of Tuesday deadly crash have yet to come out.

"We will use every means, every resource to find out what happened," Williams said. 

Also Wednesday, 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.

Philadelphia Mayor Michael Nutter said it was possible that some of the passengers listed on the train's manifest never boarded the train, while others may not have checked in with authorities. 

"We will not cease our efforts until we go through every vehicle," the mayor said, adding that rescuers had expanded the search area and were using dogs to look for victims in case someone was thrown from the wreckage.

Sumwalt 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.

Despite pressure from Congress and safety regulators, Amtrak had not installed along that section of track Positive Train Control, a technology that uses GPS, wireless radio and computers to prevent trains from going over the speed limit. Most of Amtrak's Northeast Corridor is equipped with Positive Train Control.

"Based on what we know right now, we feel that had such a system been installed in this section of track, this accident would not have occurred," Sumwalt said.

Amtrak inspected the stretch of track on Tuesday, just hours before the accident, and found no defects, the Federal Railroad Administration said. Besides the data recorder, the train had a video camera in its front end that could yield clues to what happened, Sumwalt said.

It was the nation's deadliest train accident in nearly seven years. At least 10 people remained hospitalized in critical condition late Wednesday.

Among the dead were award-winning AP video software architect Jim Gaines, a father of two; Justin Zemser, a Naval Academy midshipman from New York City; Abid Gilani, a senior vice president in Wells Fargo's commercial real estate division in New York; and Rachel Jacobs, who was commuting home to New York from her new job as CEO of the Philadelphia educational software startup ApprenNet.

Late Wednesday, a fifth victim was identified as Derrick Griffith, 42, dean of students at Medgar Evers College in Brooklyn. A statement from the college described Griffith as "a pillar in the community" who had just been granted a Doctorate of Philosophy by the City University of New York.   

Amtrak suspended all service until further notice along the Philadelphia-to-New York stretch of the nation's busiest rail corridor as investigators examined the wreckage and the tracks and gathered evidence. The shutdown snarled commutes and forced thousands of people to find other ways to reach their destinations.

The Associated Press contributed to this report. 

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