REDDING, Calif. -

Officials in Glenn County have released the official cause of death of 9 people who died in a crash involving a bus and Fed Ex truck on Interstate 5 in April.

The Glenn County Coroner's Office released autopsy results Monday for the 9 victims the department was responsible for investigating. A tenth person also died in the crash.

The report concluded that 7 of the victims died of asphyxiation due to smoke inhalation. Two others were killed by injuries sustained during the collision.

The autopsy reports will be sent to the California Highway Patrol and National Transportation Safety Board as part of their investigation.

The bus involved in the crash was one of two taking high school students from Southern California on a visit to Humboldt State University. The bus was traveling northbound just north of Orland when a southbound Fed Ex truck crossed the center divide and hit the bus head on.