By late Thursday, a 48,000-acre fire had destroyed more than 150 homes and buildings. While containment was at 20 percent, it was on course to possibly merge with the 8,200-acre fire in the national forest, where it could feed on vast stands of dead trees.

Officials have not estimated when the fires might merge, but early Friday they were about two miles apart, said California Department of Forestry spokesman Jason Goedecke.

State fire officials said that even if the fires joined, they were at least 15 miles from any areas of dead trees. But if the fires reached deadwood, authorities warned it could be bad.

"You've got 100-foot-tall trees and those are kind of like a torch," said forest spokeswoman Robin Prince.

Gov. Arnold Schwarzenegger declared a state of emergency in San Bernardino County on Thursday. The declaration will provide immediate state assistance to fire officials in need of more firefighters and equipment, and sets the stage for a request for federal disaster funding, said Eric Lamoureux, a state Office of Emergency Services spokesman.

State fire officials said late Thursday they doubted the wildfire would reach the Big Bear resort area about 8 to 10 miles away thanks to a large firebreak cleared by crews. Not taking any chances, San Bernardino County sheriff's deputies began warning residents east of Big Bear Lake, about five miles from the fire, that they should be ready to evacuate.

Dozens of homes in the Morongo Valley were ordered evacuated as flames crept down a hill a few miles away. Some residents stayed behind, their possessions in their cars, monitoring the shifting wind.

"Are we nervous? Yes. Will we stay up tonight? Yes," said Pam Bennett-Wallberg, whose 2 1/2-acre ranch serves as a refuge center for African meerkats.

A few miles away, the 8,200-acre fire was a potential threat to 75 homes. Just 5 percent contained, it was burning at higher elevations that included both brush and timber.

Authorities said smoke from the blazes 100 miles east of Los Angeles could be smelled in Las Vegas and Ogden, Utah.

Swaths of Southern California forests have been weakened by drought and killed by bark beetles. For several years, workers have been cutting down dead trees near communities and roads. Thousands of acres have been cleared but experts say it will take up to 20 years to remove all the deadwood.

The largest fire was ignited by lightning during the weekend and roared into an inferno Tuesday, racing through tiny high desert communities. Forty-five houses, 118 other buildings and 91 vehicles were destroyed in Pioneertown and other communities near Yucca Valley.

Pioneertown, established in the 1940s as a location for filming cowboy movies, lost none of its Western-style storefronts.

Elsewhere, crews were working late Thursday to contain a wildfire near Abilene, Texas, that had scorched 500 acres, forced the evacuation of a dozen homes and threatened to burn about 50 large wind turbines. In southern Montana, a group of fires estimated at 30,000 acres were 10 percent contained.