SACRAMENTO, Calif. (AP) – Investigators still have not concluded why a FedEx truck slammed into a bus full of high school students more than a year ago, killing 10. Thousands of pages of documents released Wednesday show conflicting accounts of what happened in the minutes leading up to the fiery collision.

The National Transportation Safety Board released the records Wednesday, including interviews with passengers and witnesses to the crash in April 2014 on a rural stretch of interstate highway near Orland, about 100 miles north of Sacramento.

“FedEx Driver was out head down. Saw FedEx driver slumped towards door,” a male student who sat three rows behind the driver wrote in a questionnaire from investigators.

The names of witnesses were redacted in the documents.

Investigators previously said they found no signs that the truck driver attempted to brake before the crash and that the truck left no tire marks after it veered off the southbound lanes of Interstate 5 and crashed into the bus taking students to a tour of Humboldt State University.

Five students, three adult chaperones and both drivers died.

The documents say the truck driver, 32-year-old Tim Evans, appeared to be healthy and wasn’t on the phone before the crash.

The driver of the bus had taken over for another driver in Sacramento.

However, the man who drove the bus on the first leg of the trip told investigators he did not show a standard safety video to the students and did not recall if he gave them safety instructions, possibly contributing to the chaos students described as they scrambled to escape the bus.

The agency has not reached any conclusions about the cause of the crash and did not indicate when its final report would be completed.

Copyright 2015 The Associated Press.