Fire crews battle as deadly California wildfires rage on

Firefighters battled overnight to contain wildfires in Northern California, evacuating residents in the path of 15 separate blazes that have killed at least 10 people and destroyed hundreds of homes and businesses.

Efforts to control the fires, which swept through the state's world-famous wine country, were being helped by more favorable weather conditions, a spokesman for the governor's Office of Emergency Services said.

However, the death toll could still rise, Brad Alexander warned.

"Firefighters and emergency management workers were taking advantage of the winds dying down ...and a lot of work is going to be done overnight and early (Tuesday) morning," he said late on Monday.

"...The top priority is still the evacuations for the most active fires because life protection is the number one concern."

Some 20,000 people had been evacuated from their homes since Sunday, officials said, while broadcaster CNN said more than 100 had been treated for fire-related injuries including burns and smoke inhalation.

About 1,500 homes and commercial buildings had been destroyed, Ken Pimlott, director of the California Department of Forestry and Fire Protection, said on Monday.

Fanned by high temperatures and dry conditions, the 15 fires broke out over the weekend and spread to cover some 73,000 acres (114 sq miles), fire officials said.

The largest, covering 42 sq miles and 39 sq miles respectively, struck in Napa and Sonoma counties, the heartland of California's wine industry where the status of the crop currently being harvested was unclear on Monday.

In addition to potential damage to vineyards from fire itself, experts say sustained exposure to heavy smoke can taint unpicked grapes.

Fred Oliai, 47, owner of the Alta Napa Valley Winery, said winemakers were nervous.

"You can't see anything, the smoke is very dense," he told Reuters by telephone on Monday. He had not been able to get close enough to his vineyards to see if flames reached his 90-acre property.

"We got our grapes in last week, but others still have grapes hanging," he said.

Schools and colleges near the wildfires canceled Tuesday's classes, and two hospitals in Sonoma County were forced to evacuate, state officials said.

California Governor Jerry Brown declared a state of emergency Napa, Sonoma and five other counties.

That included Orange County in Southern California, where a wildfire on Monday destroyed at least a half dozen homes in the affluent Anaheim Hills neighborhood, forcing the evacuation of hundreds of residents, authorities said.

(Additional reporting by Alex Dobuzinskis in Los Angeles, Keith Coffman in Denver, Brendan O'Brien in Milwaukee and Gina Cherelus and Joseph Ax in New York; editing by John Stonestreet)