The California Department of Forestry and Fire Protection said two civilians and nine firefighters had received minor injures and that mandatory evacuations remained in effect for part of San Bernardino County.
Only 20 percent of the fire storm had been contained while 21,000 hectares of "extremely steep rugged terrain with little access" remained in flames, the department said in a statement.
California declared a state of emergency on Thursday for southern parts of the state, with fires sweeping an area 200 kilometres east of Los Angeles.
Nearly 1,000 people were forced to evacuate their homes on Tuesday in half a dozen towns, including Pioneertown, where scores of famous Westerns have been filmed since the 1940s.
The blaze burned close to the area's renowned Joshua Tree National Park.
Officials also feared that the fire could join another, smaller fire, within striking range of mountain resorts at Big Bear Lake.
Local television images showed a wall of flames and smoke on a mountain crest a few hundred metres from a village in Morongo Valley north of the desert resort city of Palm Springs.
Lightning on Sunday started the first fire, which gained strength under a scorching sun and strong winds.
Firefighters said flames were progressing northwest and southwest toward the limits of the San Bernardino forests.