But there have been no reported injuries, Daniel Berlant, a California Department for Forestry and Fire Prevention officer, said.
"The fire's going in all directions," said Berlant. "There are reports of flame lengths over 100 feet [30 metres]."
Berlant said the fire that started on Friday was caused by a spark from a person shooting at targets and was fuelled by dry timber that had not burned for 100 years.
"There's a lot of fuel for the fire burn," he said.
About 2,000 firefighters, 200 fire engines, 12 air tankers and 12 helicopters are battling the blaze but the steep, rugged terrain is making access difficult, Berlant said.