Flames raced down a steep hillside "like a freight train," leaving smouldering remains of homes and forcing thousands to flee the wildfire churning through tinder-dry canyons in Southern California.
The fire that has destroyed at least 18 homes in northern Los Angeles County gained ferocious new power two days after it broke out, sending so much smoke in the air that planes making drops on it had to be grounded for part of the afternoon.
"For this time of year, it's the most extreme fire behaviour I've seen in my 32-year career," county fire chief Daryl Osby said on Sunday (local time).
About 482km up the coast, crews were battling another fire spanning more than 44 square kilometres that destroyed six homes on Sunday and forced evacuations outside the scenic Big Sur region.
The southern California blaze has blackened more than 88 square kilometres of brush on ridgelines near the city of Santa Clarita, and authorities found a burned body in a car.
No new measurements were available, but officials said the fire might now be double that size.
Planes were unable to make drops over the fire for a long stretch of the afternoon before resuming for a few hours before dusk. Helicopters released retardant around the perimeter of the fire all day and would continue into the night.
"The fire's just doing what it wants right now," US Forest Service spokesman Nathan Judy said. "We have to stick back, let it do what it wants to and attack it where we can."
Residents of thousands of homes were evacuated as shifting winds were pushing flames northeast through Angeles National Forest, authorities said.
The fire has ripped through brush withered by days of 37degC temperatures and years of drought.
"It started consuming houses that were non-defendable," Los Angeles County Deputy Fire Chief John Tripp said, describing the flames as charging through terrain "like a freight train".
More than 1600 firefighters were battling the flames that sent up a huge plume of smoke visible across the region.
The body of a man was discovered on Saturday in a burnt sedan outside a home in the fire zone. Los Angeles County sheriff's officials are investigating the death.
The fire destroyed film sets at Sable Ranch in Santa Clarita, which has Old West-style buildings used for movie locations.
It also forced a nonprofit sanctuary for rescued exotic creatures to evacuate 340 of its more than 400 animals, including Bengal tigers and a mountain lion.
North on the Central Coast, a blaze consuming brush in rugged mountains near Big Sur was threatening about 1650 homes.
It burned in inaccessible terrain 8km south of Garrapata State Park and forced the communities of Palo Colorado and Carmel Highlands to evacuate, California's forestry department said.