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Fast-moving fires spread by shifting winds forced thousands more Californians to evacuate their homes on Saturday as the death toll from the deadliest blaze recorded in the state's history rose to at least 40, with hundreds of people still missing.
About 10,000 firefighters supported by air tankers and helicopters overhead were battling 16 major wildfires, some encompassing several smaller merged blazes, in areas north of San Francisco that have consumed nearly 86,000 hectares over seven days, or roughly 865 sq km - an area larger than New York City.
The 38 confirmed fatalities, including 20 in Sonoma County, already make it the deadliest fire event in California history.
Some 100,000 people have been forced from their homes, including 3000 evacuated on Saturday from the city of Santa Rosa, about 80km north of San Francisco, and another 250 from nearby Sonoma city.
"This is truly one of the greatest tragedies that California has ever faced. The devastation is just unbelievable. It is a horror that no one could have imagined," California Governor Jerry Brown told a news conference in Santa Rosa.
The fires have damaged or destroyed about 5700 structures, reducing homes and businesses to ash. The fires' death toll surpassed the 29 deaths from the Griffith Park fire of 1933 in Los Angeles.
"It's an unwieldy beast right now," fire information officer Dennis Rein said at the Sonoma County Fairgrounds in Santa Rosa, the main staging area for the so-called Nuns Fire in Sonoma County, a world-renowned wine-producing region.
At least a dozen Napa Valley and Sonoma County wineries were damaged or destroyed, throwing the state's wine industry and related tourism into disarray.
For the picturesque Napa Valley town of Calistoga, the winds were a double-edged sword. The town was spared by hazardous winds when they shifted, Mayor Chris Canning said, though he warned a resurgence could pose a new threat.
The town of roughly 5000 people had been evacuated, he said.
Firefighters from states including Oregon, Washington, Arizona, Colorado and Nevada have joined crews from California to battle the blazes.
From the air, some 70 helicopters and large aircraft including a 747, two DC-10s and about a dozen air tankers doused flames across the sprawling affected area with fire retardant, officials said.
On the ground, prison inmates were helping firefighters - sometimes digging lines to help contain fires, other times preparing meals at command centers, always watched over by guard.
In an area largely dependent on immigrant farm labor, US Immigration and Customs Enforcement officials said they would temporarily suspend routine operations during the emergency, "except in the event of a serious criminal presenting a public safety threat," spokesman James Schwab said in a statement.
Ground crews gained on the wildfires on Friday, but drier weather and fast-shifting winds complicated efforts on Saturday, sparking a large new wildfire in Lake County, officials said.
The Nuns Fire, which had killed at least one person, was only 10% contained with winds threatening more residential areas, Cal Fire spokesman Antonio Negrete said.
But the more deadly Tubbs Fire, which killed at least 17 people in Sonoma County, was 44% contained, which officials considered a victory.
"It's cautious optimism, but it's optimism," Negrete said of the Tubbs Fire.
Cal Fire had estimated the fires would be contained by October 20, but Rein said they may need to revise that date because of the winds that kicked up.
US Senator Dianne Feinstein, a Democrat from California, at the news conference with the governor in Santa Rosa pledged more federal aid to the region to help it through the devastation.
Whole neighborhoods of Santa Rosa have been reduced to landscapes of ash, smoldering debris and burned-out vehicles.
Some victims were asleep when flames engulfed their homes, and many survivors had only minutes to flee.
As parts of Santa Rosa were devastated, Calistoga, about 20km to the northeast, faced hazardous winds that were forecast to push the Tubbs Fire toward town.
Mayor Canning said the shifting winds kept the flames at least 3km from the city limit.
"If the winds shift and come back again, that's a big concern," he said in a telephone interview.
All but 12 of the city's 5200 people heeded evacuation orders and left, Canning said.
"Nobody was confrontational," Canning said. "When the police or firefighters knocked on doors, most people were already ready to go with their bags packed."
With 235 people still missing on Saturday in Sonoma County alone, and rubble from thousands of incinerated dwellings yet to be searched, authorities have said the number of fatalities from the North Bay fires would likely climb.
The year's wildfire season is one of the worst in history in the United States, with nearly 3.5 million hectares burned, just behind 2012, according to the National Interagency Fire Center.