CONCORD -- An unoccupied Mt. Diablo Unified School District school bus caught fire near Willow Pass Road Friday afternoon, according to a Contra Costa Fire Protection District spokesman.

There were no students on board at the time, and no one was hurt in the incident.

The fire was reported around 2:45 p.m. It was unclear what exactly caused the fire, said George Laing, a fire inspector for the district.

Despite the plume of smoke seen by commuters, Laing said there appears to be very little damage to the bus.

Check back for updates.

Contact Katie Nelson at 925-945-4782 or follow her at Twitter.com/katienelson210.