A massive wildfire raging in California nearly doubled in size overnight, threatening 12,000 homes in a 20-mile swathe of flame and smoke and surging towards a mountaintop broadcasting complex.
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 yesterday 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 without cessation by running through steep granite canyons and feeding on scrubland that had not burned for 40 to 100 years, fire officials said.
The fire had burned 134 square miles of scrubland and trees by early this morning 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 firefighter Specialist Arnaldo Quinones, 35, of Palmdale.
In a statement, 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 half a mile away from the communications and astronomy centres on Mount Wilson, fire crews planned to set more controlled fires and 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 thriving modern centre for astronomy.
The sheer length of the fire meant that 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.