More than 1,100 firefighters have been deployed to battle the blaze, which has blackened some 35,700 acres and was zero percent contained as of Saturday afternoon.
The so-called Erskine fire, which broke out on Thursday some 40 miles (64 km) northeast of Bakersfield in Kern County, has already claimed two lives, sent three firefighters to the hospital and forced thousands of people to evacuate their homes.
More than 1,100 firefighters have been deployed to battle the blaze, which has blackened some 35,700 acres and was zero percent contained as of Saturday afternoon. California Governor Jerry Brown has declared a state of emergency for Kern County.
"It is a vicious wildfire. We are going to be committed to this for some time," Captain Tyler Townsend of the Kern County Fire Department told CNN. "A lot of communities are still in danger."
Crews were working in steep, rugged terrain, fighting flames that were fueled by hot, dry weather and brush, grass and chaparral left bone dry by California's devastating five-year drought.
Officials have not identified the two people killed in the huge conflagration, one of the worst in an already intense fire season in California. The Los Angeles Times reported that they were found together and died of smoke inhalation.
Kern County Sheriff Donny Youngblood told a Friday evening press conference that more fatalities could be discovered once authorities are able to search burned-out neighborhoods with cadaver dogs.
"My heart goes out to everyone here who has lost a home and my heart goes out to the family that perished yesterday in the fire," Sergeant Henry Bravo of the sheriff's office told evacuees at a community meeting on Saturday.
On Friday, authorities warned the more than 3,000 residents of the community of Lake Isabella on the shore of a reservoir to be prepared to evacuate.
Southeast of Lake Isabella, dozens of burned-out homes and car frames were left behind in a neighborhood reduced to a field of mangled metal and collapsed roofs.
To the south, firefighters were struggling to manage the so-called San Gabriel Complex fire in the foothills of Los Angeles County. There were two fires that started on Friday and cover a combined 5,285 acres (2,139 hectares), fire officials said. Containment was at nearly 50 percent for both blazes.