Residents are being told to get ready for a possible evacuation.
One man says he's activated the special sprinklers to dampen the roof of his house, and he's ready to leave if ordered.
The blaze was reported around 3:30 a.m. in the School Canyon area between Ventura and Ojai, about 60 miles northwest of Los Angeles, fire officials said.
At midmorning, a
"It's right in their back yard," said Joe Luna, a spokesman for the Ventura County Fire Department. "We have a lot of crews up there and are making every effort to protect those structures."
CBS' Terri Okita reports that the erratic wildfire is producing a tall barrier of flames and smoke in the hills northwest of Los Angeles. At the scene, it almost sounds like a war zone, as a fierce army of choppers and airplanes is on the attack from the sky.
Hundreds of firefighters are battling the blaze from the ground, Okita reports.
In just a few hours, the fire grew from 500 acres to 1,487 acres, said fire department spokeswoman Michele Faina. Two nearby schools were closed, and two evacuation centers were being set up. The cause of the fire was unknown.
The hilly, rocky area contains numerous oil pumps, Luna said. At least one structure had burned, apparently on an oil field, according to television footage.
Water-dropping helicopters were called in to assist hundreds of firefighters who were protecting neighborhoods. While the wind wasn't bad enough to halt the aerial attack, shifting winds and gusts up to 50 mph posed problems for fire crews.
"The winds have been problematic," Luna said. "When the winds die down, it allows us to make better progress but we expect to deal with it throughout the day."
Most of Southern California was under a red flag warning, which advises of warm, windy and dry conditions that could lead to explosive fire growth.
Forecasters expected the Santa Anas to diminish a bit in the afternoon, then increase again in the evening. Temperatures in the area were expected in the upper 70s to mid 80s. Forecasters predicted slightly lower overnight lows.
Investigators were on scene but hadn't yet determined a cause.