Around 4,000 homes and a military base on the California coast are threatened by the Springs Fire, which is still raging.
The inferno, which erupted on Thursday morning and could have been started by a discarded cigarette butt, has so far blackened 43 square miles of dry brush and shrubland.
By last night more than 950 firefighters had built containment around about 20 per cent of the blaze, north-west of Los Angeles.
More firefighters were said to be on the way and fire officials said they hoped that diminishing winds and higher humidity would help them make headway.
Fire managers said they expected it would take until next Monday to fully contain the blaze, which sent a pall of thick smoke drifting over the beach community of Malibu and farther inland across Los Angeles County.
Ventura County Fire Department spokesman Tom Kruschke said: "We're seeing fires burning like we usually see in late summer, at the height of the fire season, and it's only May."
The Springs Fire, which started less than 10 miles from the Pacific coast, spread quickly to the edges of the communities of Camarillo and Newbury Park.
By Friday morning, the flames were within a short distance of the ocean's edge in some places, forcing authorities to close several miles of Pacific Coast Highway.
At the Point Mugu US Naval Air Station on the coast, all non-essential personnel were ordered to stay home for a second day as flames encroached on a firing range at the extreme western end of the base, spokeswoman Kimberly Gearhart said.
She said no ammunition was stored at that location, bordered on two sides by coastline and wetlands.
But a base housing unit that is home to 110 active-duty military personnel and their families was evacuated on Friday because of heavy smoke, Gearhart said, adding there was no immediate fire threat to that vicinity and military aircraft were continuing routine flights between the base and a communications post on San Nicolas Island offshore.
In mid-afternoon, residents were ordered to clear out of more than 900 homes in Hidden Valley, an enclave of ranches and estate-type properties southeast of Camarillo. Some 200 homes were evacuated earlier along the coastal highway and adjacent canyon roads, sheriff's Sergeant Eric Buschow said.
Horse trainer Bryon Wilson, 36, and his wife drove two trailers into an area of multimillion-dollar ranches around Hidden Valley Road that was later ordered evacuated.
He said: "As we were loading the horses in (the trailers) this afternoon, the fire was right at the back of the barn, so we were in amongst it already."