At least 6,600 homes were under mandatory evacuation orders and more than 2,500 firefighters were battling the flames.
On the blaze’s north-western front, two firefighters were killed on Sunday when they drove off the side of a road on Mount Gleason, near the city of Acton.
The fire that has so far destroyed at least 18 homes was moving north, south and east through the rugged foothills north-east of Los Angeles.
Despite the lack of wind, it surged through steep granite canyons and feeding on scrubland that had not burned for 40 to 100 years, fire officials said.
The fire had burned 350 square kilometres of scrubland and trees yesterday and was just 5% contained. Communications and astronomy centres at the top of Mount Wilson were also threatened by fire.
The firefighters who died were Captain Tedmund Hall, 47, of San Bernardino County, and Arnald “Arnie” Quinones, 35, of Palmdale.
California governor Arnold Schwarzenegger said: “Our hearts are heavy as we are tragically reminded of the sacrifices our firefighters and their families make daily to keep us safe.” With flames about a kilometre away from the communications and astronomy centres on Mount Wilson, planes dropped fire retardant around the mountaintop complex, which holds transmitters for more than 20 television stations, many radio stations and mobile phone providers.
Television stations said if the antennas burn, broadcast signals would be affected but satellite and cable transmissions would not be.
Two giant telescopes and several multimillion-dollar university programmes are housed in the century-old Mount Wilson Observatory.
The complex of buildings is both a historic landmark and a modern centre for astronomy.
The sheer length of the fire meant it threatened homes ranging from scattered ranches to multimillion-dollar estates in luxury enclaves.
The fire was the largest of many burning up and down California after days of high temperatures and low humidity. The National Weather Service said a red flag warning for extreme fire conditions remained in effect for the mountains of central and southern California.
Rick Lund, whose house escaped the fire, stood at the end of the cul-de-sac of about 10 homes, watching firefighters attend to what once were the homes of friends and neighbours.
“It’s right there,” he said, pointing to a house of his 11-year-old daughter’s close friend. “Or it was.”