A wildfire burns out of control on the slopes of Mount Diablo in Contra Costa County, Calif., seen from the Woodbridge Ecological Reserve located in the Sacramento–San Joaquin River Delta, Sunday, Sept. 8, 2013.
CLAYTON, Calif. (AP) - A wildfire burning in a San Francisco Bay Area wilderness park grew Monday, forcing more people to leave their homes and leading to a smoke advisory for area residents.
The blaze in Mount Diablo State Park in Contra Costa County had burned 1,500 acres as of Monday morning, up from about 800 acres the previous day, according to the California Department of Forestry and Fire Protection. It was 10 percent contained.
But it was burning up the mountain, away from homes - a good sign for firefighters, officials said.
Still, roughly 25 homes were evacuated Monday morning, bringing the total to about 100.
The blaze broke out Sunday amid temperatures near triple digits in the early afternoon. The cause was under investigation.
The fire spewed a plume of smoke visible for miles. It was burning in steep, rugged terrain near Clayton, a town of about 11,000 people northeast of San Francisco, alongside the park.
In addition to the difficult terrain, firefighters faced erratic winds and continued high temperatures. But they were confident they would get the blaze under control, Cal Fire spokesman David Shew said.
"We'll get it, but it will probably be a few days," he said. Hundreds of additional firefighters were expected to join the fight Monday.
Meanwhile, an evacuation center was established at Clayton Community Library. Though not far from more densely populated parts of the Bay Area, the threatened homes were on sparsely populated properties dotted with animal pens and shooting ranges.
The Bay Area Air Quality Management District issued a smoke advisory Monday for parts of Contra Costa, Alameda and Santa Clara counties. Residents were advised to take precautions, including setting air conditioning units and car vent systems to recirculate.
Elderly people, children and those with respiratory illnesses were told to be particularly careful.