Firefighters in California faced a long battle against dozens of blazes, fed by accelerating winds and dry brush, as search-and-rescue teams started looking for bodies in parts of the state's wine country devastated by wildfires.

The entire Napa County town of Calistoga came under a mandatory evacuation order on Wednesday as authorities warned of worsening conditions driven by intensified winds. Residents were urged to leave immediately.

Authorities have barely contained the 22 fires scorching nearly 200,000 acres across eight northern California counties. The blazes have killed at least 26 people - a number likely to rise as more information emerges about the hundreds of people reported missing - and obliterated more than 3,500 homes and businesses. In Santa Rosa alone, at least 2,834 houses have fallen to the flames.

As of Thursday morning, the Tubbs Fire which was menacing Calistoga was 10 per cent contained and had scorched nearly 35,000 acres. The massive Atlas Fire had torn through nearly 45,000 acres and was only three per cent contained.

Teams have located more than 400 people reported missing and were trying to track down more than 450 people who remain unaccounted for, Sonoma County Sheriff Rob Giordano said. He acknowledged the effort was moving into a grim “recovery phase” that would involve combing through the remains of torched houses with the help of dogs trained to sniff ourt corpses.

“Identification is going to be hard”, Mr Giordano told reporters. “We have found bodies that are nothing more than ash and bones”.

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Stronger winds threaten to exacerbate the situation. After a brief respite earlier in the week from high winds that helped ignite and feed the blazes, authorities are warning that revived gusts will prolong the burning.

The National Weather Service warned of “critical fire weather conditions” ahead. Calistoga Fire Chief Steve Campbell told Reuters that his town’s fate “is going to depend on the wind”, noting that high winds had not yet blown in.

Speaking to reporters on Thursday, California Governor’s Office of Emergency Services Director Mark Ghilarducci warned that “we’re not even close to being out of this emergency”. California Department of Foresty and Fire Protection chief Ken Pimlott said “explosive” dry brush will continue to fuel blazes.

Deadly fires rage across California

That “catastrophic” struggle has spurred California to pour resources into the fight, bolstered by assistance from neighbouring states and the federal government after Donald Trump signed a major disaster declaration. California deployed more than 8,000 firefighters, along with 73 helicopters, dozens of air tankers, and over 650 fire engines. The California National Guard had mobilised thousands.

Two distinct fires have already merged and more consolidation was likely, Mr Pimlott said. He warned that weather conditions that allow fires to thrive were likely to persist through the weekend, driving volatile burns that could spur more evacuations as they abruptly shift directions or grow.

“Our fires are going to burn erratically. They have the potential to shift in any direction at any time”, Mr Pimlott said.

Local officials were working to disseminate information as they sought to rebut criticism that emergency alerts did not reach enough residents.

In Sonoma County, where evacuation orders have displaced thousands and fires have charred populated areas like Santa Rosa, authorities sent out phone numbers to locate people evacuated from two major hospitals and emphasized that people arriving at shelters would not be asked about their immigration status.