It wasn’t distracted driving that caused last month’s fatal Amtrak derailment in Washington State, according to the National Transportation Safety Board (NTSB), which has released preliminary details in what is expected to be a lengthy investigation. Exactly what did cause the accident has yet to be determined.

The Dec. 18, 2017 derailment of the Amtrak Cascades passenger train in DuPont killed three people and injured 80 more.

In its lab in Washington, D.C., the NTSB is studying information it was able to download from the lead locomotive’s event data and video recorders.

An initial review of the final portion of the accident sequence revealed the following (which the agency  warns could change as the investigation continues):

• Inward-facing video with audio captured the crew’s actions and their conversations. A forward-facing video with audio captured conditions in front of the locomotive as well as external sounds.
• The crew was not observed to use any personal electronic devices during the timeframe reviewed.
•  About six seconds prior to the derailment, the engineer made a comment regarding an over speed condition.
• The engineer’s actions were consistent with the application of the locomotive’s brakes just before the recording ended. It did not appear the engineer placed the brake handle in emergency-braking mode.
• The recording ended as the locomotive was tilting and the crew was bracing for impact.
• The final recorded speed of the locomotive was 78 mph.

A preliminary report detailing the facts and circumstances of the crash developed in this early stage of the investigation will be available on the NTSB website in the coming days.

The entire investigation is expected to last 12-24 months.