The fire had threatened half a dozen homes before moving uphill.
Crews arrived on the scene to find a brush fire burning about 3 to 5 acres. A Cal Fire spokesperson said the potential for the fire could be 400-500 acres. At 10 p.m. Thursday the fire had burned approximately 12 acres.
Some 200 firefighters were on scene as the blaze east of the Cleveland National Forest just south of Lake Elsinore.
No injuries were reported.
