(CNN)The police investigation into the Amtrak train crash is focusing on why the train's throttle was pushed forward, speeding up the train so rapidly ahead of the accident, law enforcement officials said.
Police investigation of Philadelphia train accident focusing on speed
From the very beginning, Philadelphia police were focused on the excessive speed of the train, which was going 106 miles per hour into a curve that was rated for only 50 mph, and some wanted to arrest the engineer that very first night, one law enforcement source said. But with the lead investigator, the National Transportation and Safety Board, not ruling out other potential factors like train performance, the decision was that any arrest would be premature.
An NTSB member told CNN this past weekend that the "only way" an operable train could accelerate would be for the engineer to push the throttle and the train's recorder should show that throttle movement.
"We will be looking at that to see if that corresponds to the increased in the speed of the train," NTSB board member Robert Sumwalt said in an interview that broadcast Sunday.
The engineer Brendan Bostian's experience and familiarity with the route is another key focus of investigators, a law enforcement source said.
The engineer was new to the specific Washington to New York run, a NTSB official said, having been on the route for just two weeks. But Bostian had been running trains along the northeast corridor for three years which would have included, at times, passing through this very same stretch of track.
"He felt fully qualified and comfortable with his equipment and reported no problems with his train handling," NTSB board member Sumwalt said last week. Sumwalt also said Bostian demonstrated "a very good working knowledge" of the territory and speed limitations.
CNN made multiple efforts to talk to Bostian and his attorney and seek a response to this new information but have not received a call back.
But for police investigators, the question remains why the train was so out of control if Bostian had experience in this section of track.
There have been no anomalies with the train discovered so far, a law enforcement source with direct knowledge of the investigation and a second source briefed on the investigation said. The information was relayed by the NTSB during an interagency meeting about the crash on Tuesday.
In the meantime, the Philadelphia district attorney's case could take months to build, a government source said. A law enforcement official said at best right now they only have circumstantial evidence of a reckless act and no proof that that the train was derailed intentionally. Whether criminal charges will be filed against Bostian will hinge on the NTSB's final findings, Bostian's phone records and toxicology results, the source said.
The district attorney's office has assigned its vehicular homicide investigators to the case, according to a government source. The DA would not comment on any of the evidence or progress of the investigation.
The night of the accident, police headed to the hospital to talk to those on the train. When detectives encountered the engineer he told them, " I guess you guys are looking to talk to me," one of the law enforcement officials said. Detectives then tried to question him, but he told them he didn't remember anything. At that point detectives knew how fast the train had been traveling, and when they specifically asked him how fast he was going, he told them he did not remember.
Law enforcement sources note that the engineer told the NTSB that prior to the derailment, Bostian said he was fully aware, not tired, and had no other issues. Those are the very same questions law enforcement sources say police had for him, but Bostian stopped answering questions pretty quickly and waited for a lawyer. But with no physical issues to speak of, and no fatigue, the question remains why was the train accelerating into a curve. A question which the engineer himself has been unable to answer as he says he has no memory of the incident.
On that first night, detectives also questioned the assistant conductor who said she didn't notice anything abnormal or mention any issues about hearing radio transmissions about a projectile being thrown at the train, a law enforcement official said. The assistant conductor would later tell the NTSB she overheard radio transmission between the Amtrak engineer and a SEPTA engineer mentioning rock throwing. The NTSB did not find any radio transmissions to corroborate the assistant conductors claims.
Police detectives are not giving much credence to the idea that the accident was caused by a projectile hitting the train, a law enforcement official said. The source expressed frustration the NTSB highlighted this claim so prominently especially since there is no mention of this on the Amtrak dispatch tapes.
Investigators are very interested in Bostian's online postings and looking deeper into them and the timing of the accident. As has been previously reported, in online forums for train enthusiasts, Bostian blasted the railway industry for not installing safety technology until it was mandated by Congress. The derailment happened the day before the House Appropriations committee voted on Amtrak funding.
Philadelphia police are still awaiting cell phone records to see whether he made calls, especially in the moments after the derailment. They're also looking to determine if he used his cell phone in the moments before the crash. Detectives will interview all the people he called.