California firefighters continue to battle wildfires east of San Francisco

California firefighters expected to gain ground on Sunday on a wind-driven wildfire that scorched thousands of acres 97 kilometres east of San Francisco, burned down a home and forced residents to flee the area near the central California city of Tracy.

The fire erupted on Saturday afternoon in the grassy hills managed by the Lawrence Livermore National Laboratory, one of the country's key centres for nuclear weapons science and technology. The cause was under investigation.

The California Department of Forestry and Fire Protection said the research centre was not under immediate threat from the blaze, dubbed the Corral Fire, which had devoured some 52 square kilometres by Sunday afternoon and was 30 per cent contained.

 

Thousands of people in the area, including parts of the city of Tracy with a population of 1,00,000, were ordered to leave for evacuation centres. Tracy is about 112 kilometres south of California's capital in Sacramento.

CalFire Battalion Chief Josh Silveira said on Sunday afternoon the fire "burned right up to the homes" in the area and destroyed one house. With calmer winds and milder weather Sunday, Silveira said he didn't expect the fire to grow.

Two firefighters suffered minor to moderate burns on Saturday and were expected to make a full recovery, Silveira said.

The wildfire presented no threat to any laboratory facilities or operations and had moved away from the site, Lawrence Livermore spokesperson Paul Rhien said in a statement to AP early on Sunday.

"As a precaution, we have activated our emergency operations centre to monitor the situation through the weekend," Rhien said.

Photos showed a wall of flames moving over the parched landscape as dark smoke billowed into the sky.

The wildfire also forced the closure of two major highways, including an interstate that connects the San Francisco Bay Area to San Joaquin County in central California, but they had reopened by Sunday afternoon.

The San Joaquin County Office of Emergency Services issued an evacuation order for areas west of the California Aqueduct, south of Corral Hollow Creek, west to Alameda County and south to Stanislaus County. A temporary evacuation point was established at Larch Clover Community Center in Tracy. The order was still in place as of early Sunday afternoon.

Sunday's high temperature for Tracy was expected to reach 29 degrees Celsius, with no rain in the forecast but hotter conditions are on their way.

The National Weather Service said "dangerously hot conditions" with highs of 39.4 degrees Celsius to 42.2 degrees Celsius were expected later in the week for the San Joaquin Valley, an area that encompasses Tracy. Wind gusts of up to 72 kilometres per hour lashed the region Saturday night, according to meteorologist Idamis Shoemaker of the weather service in Sacramento.