Santa Rosa, Calif. • The winds fanning wildfires in Northern California's wine-country have calmed, for now, giving firefighters a badly needed break from the "red flag" conditions that have made this menacing arc of flames so deadly and destructive.

But for localities facing relentless fires and a mounting death toll that has already reached historically grim heights, any reprieve appears remote.

As the destruction entered its fifth day, officials focused their efforts on finding the missing and the dead. Authorities continue to search for the hundreds of people who remain unaccounted for, using cadaver dogs to sniff through scorched rubble.

Twenty-nine people have died, more than half of them in Sonoma County alone. The infernos burning across the region are now the state's deadliest wildfires on record, their collective death toll equaling the 1933 Griffith Park Fire in Los Angeles that killed 29 people.

"We've found bodies that were almost completely intact; we've found bodies that are nothing more than ashes and bones," Sonoma County Sheriff Robert Giordano said at a news conference Thursday.

In some cases, bodies were only identified through ID cards or the serial number of medical devices found nearby.

"I'm sorry to have to tell you that, but that is what we're faced here, as far as identifying people and recovering people," Giordano said. "We will do everything in our power to locate all the missing people. I promise you we will handle the remains with care and get them to their loved ones."

As search and rescue teams gain access to "hot zones" that were immolated in the firestorm, officials expect to confirm more fatalities.

The death toll in Sonoma County went up to 15 on Thursday, and Giordano said it would be "unrealistic" to think it won't rise further. There were eight casualties recorded in Mendocino County, four in Yuba County and two in Napa County, according to local and state officials.

About 1,000 people have been reported missing in Sonoma County, of whom 400 remained unaccounted for as of Thursday afternoon. Giordano said search and rescue teams go to specific houses, if it's safe, to find missing persons only after they've exhausted other ways to contact them.

"We're going to that person's house in the fire zone. We're doing targeted searches ... teams of people searching for missing people," Giordano said. "That's how the majority of the recovery has been made so far."

The 21 fires currently burning across the northern part of the state have destroyed more than 3,500 buildings and torched more than 191,000 acres — a collective area nearly the size of New York City.

It is, the state's fire chief said, "a serious, critical, catastrophic event."

Thousands have fled their homes. In Sonoma County, nearly 4,000 people are at two dozen evacuation centers. Many of them will likely be unable to return home for many days, officials said. Evacuation zones also continue to expand. On Wednesday, the entire city of Calistoga in Napa County was evacuated.

"These fires are a long way from being contained, so we're doing to best we can people that have been displaced and help them to hopefully rebuild their lives" said Barry Dugan, a Sonoma County spokesman.

Nine fires are now burning in Sonoma and Napa counties, the heart of California's wine-growing industry. One of the biggest and by far the deadliest, the Tubbs Fire in Sonoma grew about 6,000 acres overnight before conditions began to improve.

The National Weather Service said the calmer winds will last through Friday, giving fire crews a slim chance against the blazes that have mostly raged uncontrolled. But dry conditions, coupled with a new round of high winds expected this weekend, could further hamper containment efforts, officials said.

In many areas, crews have been working for days straight.

Keith Muelheim, Mike Stornetta and Jason Jones, firefighters in the town of Windsor in Sonoma County, estimated that they had been awake for more than 70 hours and did not eat for the first 16.

For them, the Tubbs Fire is a personal one.

Stornetta's parents lost their house of 30 years, the house where he grew up, as a firestorm swept through their Santa Rosa neighborhood earlier this week.

"Our first assignment was two blocks away," he said during a patrol. "While we were evacuating an elderly care facility home, we could see down into the glow of the neighborhood where I knew my parents lived."

His parents were not home, Stornetta said, but his grandmother was housesitting and just barely escaped. His family lost everything, except the clothes they were wearing.

For Capt. Greg McCollum of the Santa Rosa Fire Department, the sheer size and power of the Tubbs Fire has humbled him after 24 years on the job.

"This is a once-in-a-career fire," he said. "One of the other guys said it's a once-in-two-careers fire. Well, I'm no historian, but I know a damn big fire when I see one."

As thousands of firefighters work to contain the blazes, officials have started looking at what's ahead: Cleaning up the charred remains of thousands of structures, some of which could contain potentially hazardous materials.

"You can imagine what it's going to take," said Dugan, the Sonoma County spokesman. "You just take one area in Santa Rosa, the Coffey Park area. There's dozens if not hundreds of [destroyed] homes. That's a lot of cleanup and a lot of debris. Once the fire is under control, there'll still a lot of work to do."

He added: "This is going to be months and years of recovery for the county."

Amid these grim bulletins, the huge utility company PG&E acknowledged that the extreme winds late Sunday and early Monday had knocked trees into power lines in conditions conducive to wildfires.

"The historic wind event that swept across PG&E's service area late Sunday and early Monday packed hurricane-strength winds in excess of 75 mph in some cases," said Ari Vanrenen, a PG&E spokeswoman, in a statement released after the San Jose Mercury News first reported on a possible link between the wildfires and the power grid.

"These destructive winds, along with millions of trees weakened by years of drought and recent renewed vegetation growth from winter storms, all contributed to some trees, branches and debris impacting our electric lines across the North Bay," she said.

Mike Mohler, a Cal Fire battalion chief, said investigators are looking into a series of calls about infrastructure failure and downed power lines Sunday night in Sonoma County - and whether those may have caused some of the fires.

"Investigators are out there, trying to determine exactly if lines were down, how many and where they were," Mohler said.

PG&E has said that hundreds of its employees have been working with Cal Fire by de-energizing some power lines to help with response efforts, the company said in a statement.

The utility company issued repeated warnings to its customers once heavy winds started battering the region Sunday morning. "High winds expected. Be alert near fallen trees/branches. Report downed lines to 911," PG&E tweeted several times.

Officials with the California Department of Forestry and Fire Protection (Cal Fire) said they have yet to determine the cause of the fires.

Statewide, 8,000 firefighters are working to contain the fires, the worst of which are in Mendocino, Napa and Sonoma counties. In Sonoma County alone, more than a half-dozen separate wildfires have flared up and fanned out, including one that started Wednesday.

Families crowd areas off the highway, their cars packed with belongings. Highway 101 cuts through rolling hills that dominate the California coast, and entire landscapes are scarred black. In Santa Rosa, it is possible to trace the direction of the wind by which buildings were reduced to ashes and which remained untouched.

On Wednesday, Ameir Kazemi stared at the smoldering remains of his business, Mohawk Sign. It has been a Santa Rosa institution for 50 years, and Kazemi, 33, has owned it for a decade. Now, it's a pile of ashes and charred wood.

For several hours on Monday, Kazemi said local TV stations broadcast videos of his building on fire.

"It was pretty sickening," he said. "I just wanted to come see if there was any chance that anything survived - the artwork, 10 years' worth of stuff on my hard drive. It's all gone."

The fires have put a strain on federal resources, too. Coming on the heels of a string of catastrophic hurricanes, the California wildfires in total represent just one of 22 disasters that the Federal Emergency Management Agency is managing across the nation. Eighty-five percent of FEMA's 9,900 full-time employees are working "in the field," away from their assigned offices, agency spokesman Mike Cappannari said.

Staff writers Kristine Phillips, Abigail Hauslohner and Aaron C. Davis contributed to this report.