SANTA BARBARA, Calif. (AP) - The third-largest wildfire in modern state history showed no sign of slowing down, as hot and dry conditions helped sustain the blaze raging through a vast swath of rugged wilderness.

The wildfire has blackened 337 square miles, or about 215,000 acres, in Los Padres National Forest backcountry since starting July 4. It was 77 percent contained today.

Firefighters faced rugged terrain, temperatures in the 90s and extremely low humidity in the wilderness area that hadn't burned in 75 to 100 years, fire officials said.

“The fuel conditions are extreme. The chaparral we're working with is practically explosive,” said incident commander Mike Dietrich of the U.S. Forest Service.

As a precaution, residents of 30 to 40 ranches in Santa Barbara and Ventura counties were advised to move large animals out of the area and be prepared to get out themselves. A 45-mile stretch of the highway was closed.

“They are trying to corral the fire away from them,” fire spokesman Victor Gutierrez said Monday, noting firefighters were using backfires to eliminate fuel and starve flames.

The fire was still 17 air miles north of the Ventura County community of Ojai and 10 miles east of Montecito and Carpinteria in Santa Barbara County, Gutierrez said.

Gov. Arnold Schwarzenegger declared a state of emergency Sunday for Ventura County, clearing the way for state government cost assistance.

Sparks from equipment being used to repair a water pipe ignited the blaze north of Los Olivos on July 4. Firefighting costs have exceeded $85 million.

The state's biggest wildfire was the 2003 Cedar Fire near San Diego, which burned more than 273,000 acres, destroyed 4,847 structures and killed 15 people.

In 1932, the Matilija Fire burned about 220,000 acres in the Los Padres National Forest, near the current Zaca blaze.