WILLOWS, Calif. » Authorities have released the cause of death for nine of the 10 victims of a Northern California crash between a charter bus full of students and a FedEx tractor-trailer.

Glenn County Sheriff Larry Jones said Monday that seven of the victims in April’s crash succumbed from asphyxiation due to smoke inhalation. Two others died of multiple traumas from the collision.

The cause of death for a 10th victim was being handled by Sacramento County medical examiners. Jones said that person died at a hospital burn unit.

The bus was carrying 44 students from Southern California for a free tour of Humboldt State University on the state’s far north coast. Many were hoping to be the first in their families to attend college. Five students and three adult chaperones died, along with the drivers.

The cause of the crash is under investigation.