Fire driven by Santa Ana winds spread over 30 acres of brush in steep terrain Monday, threatening 20 homes.

Wind was blowing the fire through hills in a southerly direction a short distance south of U.S. 101, said Ventura County fire Capt. Barry Parker. The blaze, burning in the Thousand Oaks area, was 15 percent contained late Monday.

"The fire is being pushed by mild Santa Ana winds. It's staying within its perimeter so that's a good thing," Parker said.

More than 200 firefighters were on the lines and two helicopters made water drops over the area of modern homes, many set in cul de sacs amid hills.

The cause of the fire was under investigation.

The blaze broke out as "red flag" warnings were posted for fire danger due to gusty offshore winds and low humidity levels in Ventura County and parts of neighboring Los Angeles County. Santa Anas blow from the interior of the West toward the coast, pushing back the normal flow of moist air off the Pacific.

The Ventura County Fire Department closed its fire season on Jan. 15, citing forecast weather patterns with reduced potential for major wildland fires. Just last week, a storm blew through, delivering rare snow to the nearby Santa Monica Mountains above Malibu.

The closure of fire season involves changes in work schedules and equipment. The department warned, however, that there is year-round fire danger in Southern California.

Thousand Oaks, with a population of 127,000, is about 40 miles west of downtown Los Angeles.

Earlier this month, a wind-driven brush fire roared through an exclusive beachside area in Malibu, destroying five homes including one belonging to Suzanne Somers and damaging six others. Losses have been estimated at $60 million.