A fire near Mt. Diablo, about 35 miles east of Oakland, has grown past 800 acres and is 10 percent contained, according to Cal Fire. The fire is still growing.
A strike team of engines from San Ramon Valley Fire and the Contra Costa County Fire Protection District responded for structure protection.
The response includes: 25 engines, 4 air tankers, 2 helicopters, 6 crews, 4 bulldozers, per CalFire.
About 50-75 structures are threatened by the fire.
Homes on Curry Canyon Road and Oak Hill Lane are under mandatory evacuation. Some homeowners were on top of their roofs spraying them down.
Homeowners have been asked to head to the Clayton Community Library at 6125 Clayton Road for shelter. Volunteers are there and have food and water for anyone who needs it.
Clayton resident Andy Cuellar said he was concerned about what could happen.
"There's 60 acres of open land behind my house, 40 acres of open land on the other side of my house and if a spot fire hits either one of those two properties, then I'm kind of sandwiched in between," Cuellar said. "That's the fate of most of us who live out here."
Those with disabilities who are not able to leave their homes on their own should call 911 immediately, according to the Contra Costa Sheriff's Department.
CalFire said it expects the fire to continue to grow for two reasons--weather conditions and firing operations, which are fires CalFire is setting in an attempt to steer the fire into terrain that isn't as steep.
Throughout the day, a massive plume of smoke could be seen from all over the Bay Area, including by people driving across the Bay Bridge. The fire started at about 1 p.m. Sunday.