By Mark Abrams

PHILADELPHIA (CBS) — Federal investigators say they’re making progress in their probe into what may have caused the Amtrak train derailment Tuesday night in Philadelphia.

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National Transportation Safety Board member Robert Sumwalt, who is leading the investigation, says in the wake of preliminary information that the train was running in excess of 100 miles an hour going into a curve, more data has been revealed in an on-board camera from the front of the engine. Sumwalt says it captured the final fateful minutes before the engine and its seven cars went tumbling off the tracks.

“Thirty-one seconds before the end of the recording, the train speed was going through 90 miles per hour. Sixteen seconds before the end of the recording, the train speed was going through 100 miles per hour,” said Sumwalt.

Sumwalt said the train increased its speed by 30 miles per hour in 49 seconds. The train peaked at 106 miles per hour and was clocked at 102 miles per hour when it crashed.

Sumwalt wouldn’t say who or what was causing the train to accelerate, even though the speed at that area was only 50 miles per hour.

“We always look at distraction. We always look at potential for fatigue,” Sumwalt said.

The NTSB official also confirmed that the train engineer, Brandon Bostian, has agreed to be interviewed by federal investigators and will be asked to provide his own account of what happened the night of the derailment.

Sumwalt said the NTSB is expected to meet with Bostian over the next few days.

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“If I were interviewing him, what I would wanna do is actually not ask questions. I would just want to just figuratively give him a clean sheet of paper and say ‘tell us what happened,’” Sumwalt told Eyewitness News.

In online postings, a user who appears Bostian was often critical of the railroad industry for failing to implement safeguards against human error.

A posting from 2011 read: “At any point over the previous eighty years the railroad could have voluntarily implemented some form of this technology.”

Bostian’s attorney contends his client doesn’t even remember the crash and said he suffered a concussion. In addition, Bostian’s attorney said his client gave a blood sample and cell phone records to investigators.

Earlier in the day Thursday, the eighth and final victim was recovered by firefighters from the heavily damaged first passenger car, putting the death toll at eight.

Mayor Michael Nutter also confirmed that all 243 passengers on board Amtrak Train 188 have been accounted for, with more than three dozen still hospitalized.

Amtrak’s CEO pledged the rail operator would have speed regulation technology installed and functioning by the end of the year along the Northeast Corridor, which runs through Philadelphia.

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Sumwalt says he believes had that technology been in place, the accident probably wouldn’t have happened.