The Peak Fire, on Old Waterman Canyon Road off of Highway 18 near San Bernardino, is burning 34 acres.
The fire is reported to have been triggered by a BMW crashing on a mountain road. The fire appears to be slowing its spread. About 150 firefighters are fighting the blaze and 14 pieces of aircraft.
The cause is under investigation.
Both U.S. Forest Service firefighters, along with the San Bernardino County Fire department, have responded to the fire.
One structure has been threatened but there are no evacuations.
Officials say Highway 18 will be closed for several hours.