The bus was on its way to Yakima, Washington from Los Angeles with stops along the way.
More than 30 people were on board the bus -- 16 of them suffered minor injuries. The driver of the semi-truck also suffered minor injuries. Nine people were taken to the hospital for treatment.
The CHP is investigating, but it appears the bus rear-ended the big-rig when the semi hit the brakes. Others on the bus who were not injured were transferred to another bus to continue their northbound trip.