A van was found overturned in a drainage ditch in unincorporated Contra Costa County on Sunday morning and the driver had to be airlifted for medical treatment, according to fire officials.

East Contra Costa Fire Protection District officials said a report came in about the single-vehicle crash at 10:03 a.m. Sunday at Sandmound Boulevard and Bethel Island Road near Oakley.

A van was found on its side in a drainage ditch, fire officials said. The driver involved had a leg pinned under the van and had to be extricated.

The driver, who fire officials said was not wearing a seatbelt, was suffering possible head and internal injuries and had to be flown to John Muir Medical Center in Walnut Creek.

The California Highway Patrol is investigating the crash. CHP officials were not immediately able to provide further details.