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LOS ANGELES — A growing brush fire was threatening thousands of homes in Brentwood and other hillside communities on the west side of Los Angeles, burning homes and prompting widespread evacuations early Monday.

The Getty fire broke out shortly after 1:30 a.m. along the 405 Freeway near the Getty Center and spread to the south and west, rapidly burning more than 500 acres and sending people fleeing from their homes in the dark. About 10,000 structures have been placed under mandatory evacuation orders.

The evacuation zone was described by fire officials as a box: Mulholland Drive on the north side, the 405 on the east, Sunset Boulevard on the south and Temescal Canyon Road on the west.

Los Angeles Fire Department Chief Ralph Terrazas said despite firefighters’ efforts, at least five homes, including some on Tigertail Road, have been destroyed in the blaze. That number likely will climb in the coming hours.

Mayor Eric Garcetti urged residents to leave if they are under mandatory evacuation orders, saying some have had only 15 minutes to flee.

“Get out when we say get out,” he said, urging homeowners to not try to fight the fire with garden hoses. “The only thing you cannot replace is you and your family.”

The roughly 500 firefighters battling the blaze early Monday braced for a challenging fight as fire weather conditions are expected to worsen through the day. Pre-dawn, embers were being cast a mile ahead of the body of the fire amid moderate winds. Thick smoke was visible across the Los Angeles Basin.

Fire officials advised residents outside the mandatory evacuation zone but in the fire area to prepare to leave. UCLA and other areas east of the 405 are not under an evacuation warning.