A wildfire in Los Padres National Forest that spread to 7,500 acres by Saturday night is under attack by more than 1,500 firefighters, including 20 from the Ventura County Fire Department.

Tony Guzman, a spokesman for the California Department of Forestry and Fire Protection, said that the fire in Santa Barbara County is in a steep, remote area of oak woodlands and moving in a northeasterly direction.

"It's getting bigger," he said. It was 15 percent contained by late Saturday.

The local firefighting contingent sent north to help battle the blaze included a strike team, two bulldozers and a battalion chief, said Chris Horst, a dispatcher with the Ventura County Fire Department.

Oxnard Fire Department Battalion Chief Darwin Base said Saturday that two of the department's fire engines and a crew of six are on standby and will probably respond if the blaze threatens structures in the area.

"We are a very aggressive department," Base said.

The fire broke out Wednesday 15 miles north of Los Olivos, and it was showing no signs of slowing down Saturday as it burned through chaparral that had not seen flames for about 40 years. So far, no structures have burned.

Residents of the few ranches in the area have chosen to stay in their homes rather than leave, Santa Barbara Fire Capt. Eli Iskow said. The fire also threatened some campgrounds and the historic Manzana schoolhouse, a century-old wooden building, Iskow said.

The 1,537 firefighters on the line battled flames by hand or with bulldozers and were aided by nearly two dozen aircraft, including 15 helicopters, according to Guzman.

Eleven crew members have been treated for heat exhaustion or minor injuries since the blaze began.

Temperatures were expected to be in the high 80s to mid-90s, and humidity remained low Saturday.

Base said recent hot temperatures and lingering dry spells are the catalyst that create a "high potential" for fires in Ventura County and Southern California.

He said it is always good to have as many firefighters on a large blaze as possible to relieve exhausted crews who need a break. Usually, Base said, firefighters battling wildfires work one day and are off the next.

They are working three or four days a week and as many as 12 to 15 hours at a stretch, he said. Also, when a fire is growing and there aren't enough people available to fight it, firefighters can work a nonstop 24-hour shift, he said.

Grinding equipment sparks fire

The Los Padres fire was ignited by sparks from grinding equipment as workers repaired a water pipe on private property. Roads in the fire area were closed along with portions of the wilderness area.

Another brush fire in the Antelope Valley grew to 500 acres Saturday evening, jumping a freeway and threatening homes, according to Capt. Mike Brown of the Los Angeles County Fire Department.

Residents of about 40 nearby homes evacuated voluntarily, and a shelter was set up at a nearby high school, he said.

That fire was reported just after 2:30 p.m. along the 14 Freeway south of Agua Dulce Canyon Road and near Vasquez Rocks County Park. The California Highway Patrol closed the freeway between Shadow Pines Boulevard and Escondido Canyon Road.

About 300 firefighters were battling the blaze, and officials were hopeful that cooler evening temperatures and calmer winds would aid in the fight, Brown said.

Three wildfires ignited by a lightning storm were also spreading quickly Saturday through a popular wilderness park in the Sierra's eastern front, forcing the evacuation of at least 200 people from the small town of Independence, officials said.

500 firefighters battle blaze

No injuries or fatalities had been reported, but more than 500 firefighters were battling the blaze, which consumed at least 17,000 acres of the 2 million-acre Inyo National Forest, said forest spokeswoman Nancy Upham.

An evacuation center has been set up in Lone Pine, about 16 miles south of Independence. No other towns were threatened by the blaze, Upham said, and no further evacuations were expected.

Firefighters were also searching for and evacuating an unknown number of day hikers and overnight backpackers. The blazes were completely uncontained, she said.

Highway 395, which runs along the eastern spine of the mountain range, was closed for a few hours Saturday, but officials were escorting drivers back down the road Saturday evening.

Many smaller roads leading from the highway into the mountains were also closed. Numerous campgrounds and a lodge had been evacuated, Upham said.

Meanwhile, nearly 300 miles north in the Plumas National Forest, a lightning storm Thursday also sparked wildfires that had already torched 11,500 acres and were expected to consume more brush Saturday.

— Staff writer Raul Hernandez contributed to this report.