SAN LUIS OBISPO, Calif. (AP) - Hundreds of firefighters and a fleet of air tankers and helicopters on Monday battled flames that have burned nearly 8 square miles of wilderness in California's midsection.

No one has been hurt, but an 1800s-era Kern County cattle branding camp was destroyed as the wildfire raged untamed across grassland on a westward run from an oil field to a rugged, remote mountain area of eastern San Luis Obispo County.

Some 600 firefighters from as far away as Sacramento and San Diego were on the fire lines, Kern County fire spokesman Leland Davis said. Four air tankers and five helicopters made sorties with retardant and water drops.

The California Department of Forestry and Fire Protection said the 5,068-acre blaze was 20 percent contained at dawn. There was no estimate for full containment.

Fire bosses said they were giving all they've got to snuff the flames before the arrival of a hot, dry weather system that c ould bring 25 mph winds. Temperatures were expected near 100 degrees Monday with humidity levels of 14 percent, Davis said.

The blaze started at 10:15 a.m. Sunday in the McDonald-Anticline Oil Field and flames quickly moved west into San Luis Obispo County's Temblor Range, some 20 miles southwest of Lost Hills. The cause of the fire hadn't been determined.

After crackling through dense, 5-foot stands of grass in the San Joaquin Valley, the fire moved into the rugged hills and mountain areas east of San Luis Obispo. Vegetation has grown dramatically in recent months because of heavy winter and spring rain.

"It's rugged, steep terrain. The grass is very thick and the rattlesnakes - large rattlesnakes - are out there in full force," Davis said.



Copyright 2011 The Associated Press.