The death toll from the derailment of a passenger train in Philadelphia rose to eight Thursday with the discovery of a body in the wreckage, as investigators focused on the actions of the engineer in the run-up to the crash.

All 243 people who were aboard the train late Tuesday when it ran off the rails, leaving some cars overturned and reducing others to twisted heaps of metal and debris, have now been accounted for, officials said.

Amtrak Train 188, which was traveling from Washington to New York, crashed as it entered a curve while moving at a little over 100 miles (160 kilometers) per hour -- double the 50 mph speed limit, according to investigators.

The compromised state of some of the cars left rescuers with a difficult job ensuring all bodies had been removed.

Philadelphia Fire Commissioner Derrick Sawyer said recovery workers found the body with the help of a cadaver-sniffing dog. The victim's identity was not released.

"We have confirmed eight deceased from this horrible tragedy," Mayor Michael Nutter told reporters.

"But all individuals that we had any reason to believe were on that train have now been accounted for, and we know their whereabouts completely."

Besides the eight fatalities, more than 200 people were injured in the wreck.

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'Reckless' train driver'

Nutter had previously described the actions of the train driver, identified by US media as 32-year-old Brandon Bostian, as "reckless" but on Thursday distanced himself somewhat from the remark and said he was merely being "expressive."

"But I don't think that any common sense, rational person thinks that it was okay to travel at that level of speed, knowing that there was a pretty significant restriction on how fast you could go through that turn," Nutter said.

Bostian's attorney Robert Goggin told ABC News on Wednesday night that Bostian had no explanation for the crash and no recollection of it either.

Bostian has provided a blood sample, turned over his cell phone and is cooperating with authorities, Goggin said, according to ABC.

Bostian "was interviewed by the police department, but I believe it was a pretty short interview in which he apparently indicated that he did not want to be interviewed," Nutter said.

"He doesn't have to be interviewed if he doesn't want to at this particular stage -- that's kind of how the system works."

Investigators recovered the train's "black box" data recorders but the National Transportation Safety Board has cautioned that its first assessment of the data was preliminary, and that it would need more time to piece together what happened.

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Amtrak Train 188 derails in Philadelphia

Experts and some lawmakers say the crash could have been avoided if Amtrak had fully implemented a high-tech backup system called Positive Train Control, which prevents trains from speeding or going through red lights.

Though Amtrak has been installing the system for years across its vast rail network, the stretch of track where the crash occurred was not covered.

"We had to change a lot of things on the corridor to make it work, and we're very close," Amtrak chief executive Joseph Boardman told reporters.