LOS ANGELES (CNS) - Fire officials say the mission of crews battling the Skirball Fire in the Sepulveda Pass and Bel-Air today is to prevent the eastward expansion of a blaze that has destroyed four homes, damaged 12 others and prompted the evacuation of thousands.

Crews will continue to work against Santa Ana winds today, which Cal Fire officials said are expected to reach 80 mph at their peak.

The non-injury blaze, which was reported at 4:52 a.m. Wednesday on the east side of the San Diego (405) Freeway near Mulholland Drive and prompted a morning rush hour closure on the freeway, was estimated to have scorched at least 475 acres and was 20 percent contained as of Thursday morning, according to the Los Angeles Fire Department.

The fire was kept to the east side of the freeway and with winds easing, the forward movement of the fire was halted, but firefighters were in a desperate race to contain the blaze before a new round of strong wind gusts today, said LAFD Deputy Chief Charles Butler.

About 700 homes and an apartment building were evacuated. One elementary school was also evacuated, Butler said. All evacuations remained in place Thursday.

Aircraft crews, engine companies and hand crews were at work battling the fire, with more than 300 firefighters deployed, Butler said.

Six fixed-wing aircraft and a number of helicopters also were deployed, Los Angeles Mayor Garcetti said in a news briefing Wednesday.

LAFD Chief Ralph Terrazas said red flag conditions are expected to remain in effect through the rest of the week, with gusting Santa Ana winds presenting a continuing danger of rapidly spreading blazes.

Other agencies assisting include the U.S. Forest Service, Los Angeles County Fire Department and Cal Fire.

The Getty Center and the nearby Skirball Center, both on the west side of the freeway, did not appear to be threatened, though both will remain closed today.

UCLA, Cal State Northridge, Los Angeles Valley College and Santa Monica College have canceled classes for today.

All Los Angeles Unified School District schools in the San Fernando Valley and some on the Westside of Los Angeles -- a total of 265 district schools and charter schools -- will be closed today and Friday, district officials said. A full list of closed schools is available at www.lausd.net.

The Santa Monica Malibu Unified School District closed all of its schools Wednesday and today. It was unclear if those campuses would reopen on Friday.

Shortly after 6 a.m. Wednesday, mandatory evacuations were ordered for Moraga Drive, Linda Flora Drive, and Casiano Road, down to Bellagio Road, according to the LAFD. The evacuation order was later expanded, covering a large area bounded by Mulholland Drive to the north, Sunset Boulevard to the south, the 405 to the west and Roscomare Road on the east.

The exception to the evacuation order was the Bel-Air Crest housing development, which was not threatened, Garcetti said.

About 100 officers from the Los Angeles Police Department were sent to the neighborhood to handle evacuation orders, said LAPD Chief Charlie Beck.

Evacuation centers have been established at Delano Recreation Center, 15100 Erwin St., Van Nuys; Balboa RC, 17015 Burbank Blvd., Van Nuys; Sherman Oaks RC, 14201 Huston St., Sherman Oaks; and Westwood RC, 1350 Sepulveda Blvd., Westwood.

The fire was burning in the same general area as the devastating Bel- Air Fire of 1961. That blaze destroyed about 500 homes and led to various policy changes, including a prohibition on wood-shingle roofs and the strict requirement to remove brush from around properties.

Photo: Getty Images