SONOMA, California — Search-and-rescue teams, some with cadaver dogs, started looking for bodies Thursday in parts of California wine country devastated by wildfires, authorities said, sounding a warning that more dead were almost sure to emerge from the charred ruins.
At least 31 people have died and some 3,500 homes and businesses have been destroyed by the blazes, which were well on their way to becoming the deadliest and most destructive in California history.
Sonoma County Sheriff Robert Giordano said officials were still investigating hundreds of reports of missing people and that recovery teams would soon begin conducting "targeted searches" for specific residents at their last known addresses.
"We have found bodies almost completely intact, and we have found bodies that were nothing more than ash and bones," the sheriff said.
Some remains have been identified using medical devices that turned up in the scorched heaps that were once homes.
"There have been IDs in this case, in a pile of ash and bone, where there was a piece of metal left from somebody's surgery, like a hip replacement, with an ID number that helped us identify the person," he said.
Winds up to 45 mph (72 kph) were expected Thursday in areas north of San Francisco and stronger, more erratic wind gusts were forecast for Friday. Those conditions could erase modest gains made by firefighters.
"We are not out of this emergency. We are not even close to being out of this emergency," Emergency Operations Director Mark Ghilarducci told a news conference Thursday.
More than 8,000 firefighters were battling the blazes and more manpower and equipment was pouring in from across the country and from as far as Australia and Canada, officials said.
The ferocious fires that started Sunday leveled entire neighborhoods in parts of Sonoma and Napa counties. In anticipation of the next round of flames, entire cities evacuated, leaving their streets empty, with the only motion coming from ashes falling like snowflakes.
Fire officials are investigating downed power lines and other utility equipment failures as possible causes of the fires, said California Department of Forestry and Fire Protection spokeswoman Janet Upton. She said it's unclear if downed power lines and live wires resulted from fires or started them.
Jennifer Robison of Pacific Gas and Electric Co. says the utility is focused on restoring power and maintaining safety. She says they will not speculate about the causes of the fires.
An estimated 25,000 people have been driven from their homes by the flames, officials said. A few left behind cookies for firefighters and signs reading, "Please save our home!"
In Calistoga, a historic resort town known for wine tastings and hot springs, 5,300 people were under evacuation orders.
As the wildfires raged for a fourth day, they have continued to grow in size and cross county lines. A total count of 22 fires on Wednesday changed to 21 on Thursday because two large fires had merged together, said state Fire Chief Ken Pimlott.
Many burned out of control, spanning more than 304 square miles (787 square kilometers), an area that if taken together was equivalent to the size of New York City's five boroughs.
Strategic attacks that have curbed destruction and death tolls in recent years have not worked against the ferocity of the blazes.
Officials say fire crews have some progress on the deadliest fire in Sonoma County, bringing containment to 10 percent.
The ash rained down on Sonoma Valley, covering windshields, as winds picked up. Countless emergency vehicles hurried toward the flames, sirens blaring, as evacuees sped away after jamming possessions into their cars and filling their gas tanks.
Helicopters and air tankers assisted thousands of firefighters who were trying to beat back the flames. Until now, the efforts have focused on "life safety" rather than extinguishing the blazes, partly because the flames were shifting with winds and targeting communities without warning.
In Southern California, cooler weather and moist ocean air helped firefighters gain ground against a wildfire that has scorched nearly 14 square miles (36 sq. kilometers).
Orange County fire officials said the blaze was 60 percent contained.
Gecker reported from San Francisco. Associated Press writers Olga R. Rodriguez, Andrew Dalton and Juliet Williams Dalton in San Francisco contributed to this report.