The National Transportation Safety Board has wrapped up its investigative phase of last year's fatal Amtrak train 188 derailment and now the documents pertaining to the crash are poised to be released, which may shed light on the incident that left eight people dead and more than 200 injured.

Investigators have already released considerable amounts of information about the crash, such as the train's data recorder which shows that it was travelling about twice the speed limit of 50 mph prior to the crash. However, new information, such as the transcript of the interview with Amtrak 188 engineer, 32-year-old Brandon Bostian, will also be revealed, according to CBS Philadelphia.

Bostain was interviewed by federal authorities on May 15, and NTSB board member Robert Zumwalt talked about what they learned.

"Our investigators found the engineer to be extremely cooperative," he said. "He was accompanied by his lawyer, which is not at all unusual. And the engineer encouraged us to contact him further, again, contact him again, if we needed anything else."

Bostain's testimony ultimately didn't help the investigators why the train was going at 100+ mph as it entered Frankfort Junction, since he alleged that he didn't remember much about the incident since he hit his head in the crash, according to the Associated Press.

Investigators found evidence that a rock or another projectile, like a bullet, hit the windshield of the engine just before the derailment occurred and while an investigation did find that something did strike the window, they declined to speculate on whether it had any bearing on the crash.

With dry holes turning up on every avenue of investigation, the NTSB will use the released documents to prepare a report on the probable cause of the derailment and make safety recommendations.

A final report is not expected until later this year, likely around the May 12 anniversary of the crash.

The NTSB has a dedicated website for the investigation which can be viewed here.