A massive California wildfire marched toward a mountain resort town and a parched national forest today, threatening to combine with a second blaze in what state officials called a "very critical" situation.
Governor Arnold Schwarzenegger declared a state of emergency for San Bernardino County as a result of the wildfires.
Crews tried to establish battle lines at the western edge of the raging fire - which has already blackened more than 40,000 acres (16,190 hectares) and destroyed nearly 100 buildings in the California desert north of Palm Springs - before it reached the mountain community of Big Bear Lake.
State officials also worried about the wind-fueled flames reaching stands of dead trees in the San Bernadino National Forest and the possibly explosive result of a meeting between the huge fire and a 2,000-acre (810-ha) blaze burning nearby.
"It will be an intense situation," California Department of Forestry spokeswoman Karen Guillemin said of the two fires merging. "There will be a tremendous amount of fuel on fire and a lot of energy being released at one time. The situation here is very critical."
The so-called Sawtooth fire, which was ignited by lightning strikes on Sunday, was moving very quickly, fueled by temperatures near 100 degrees (38 C), humidity below 20 percent and hot gusts of wind.
The blaze, which 1,300 firefighters struggled to contain, produced huge plumes of black and gray smoke visible as far away as Nevada. "The things that are burning here - plants trees, shrubs - everything is very dry," Ms Guillemin said.
"There's been a drought in the area and the moisture levels are critically low. It's a major heads-up situation for firefighters."
Ms Guillemin said crews were optimistic that they could prevent the fire from reaching the Big Bear area but worried about the flames reaching the national forest, which had been hit hard by beetle infestations.
"There are some major bug kill areas in the forest where 80 to 100 per cent of the trees are dead," she said. "If the fire started in (one of those areas of the forest) it would be almost impossible to stop."
Mandatory evacuations were in place for at least five communities with residents of other areas being advised of danger.
Ms Guillemin said more than 3,000 structures were considered threatened. In the area evacuated was Pioneertown, a tourist attraction that has served as the backdrop for Hollywood westerns since the 1950s.