Authorities said Wednesday afternoon that the fire surged from 220 acres to about 400 acres in less than an hour. The fire is 20 percent contained.
It broke out about 11:30 a.m. Wednesday in Murrieta, about 90 miles southeast of Los Angeles. Its cause is not known.
Air tankers, several helicopters and more than 150 firefighters were on scene to stave off flames that were creeping toward several large hillside homes.
The blaze enveloped one large, two-story home on Wednesday afternoon. Television images showed the flames leaping out of the home's roof as plumes of grey smoke blanked surrounding hillsides.
