CONTRA COAST COUNTY, CA (NBC News) – Fire officials say there’s no end in sight in the battle against a string of deadly wildfires burning across Northern California.

At least 31 people have been killed by the fires since Monday. Hundreds more are still unaccounted for. More than 4,000 buildings have burned, leaving tens of thousands homeless.

“I didn’t know what gone meant until I saw it, like nothing left,” said Contra Coast County Fire Captain Chris Christiansen as he surveyed the ashes that remain where his own home once stood.

Sonoma County deputies are working to recover bodies from incinerated homes, a grim and difficult task made even harder by the intensity of the fires.

“Some of these remains are actually intact bodies. Much easier to identify. Much easier to get things from,” said Sheriff Rob Giordano. “Some of them are merely ashes and bones. We may never get truly confirmative identification on ashes.”

Authorities told NBC News that nearly 400 people are still missing, but it is unclear how many on the missing list are duplicates or even people who are actually safe.

Harsh weather conditions are only making the fight against the fires more difficult. Overnight temperatures have remained high, while the humidity has remained low, and high winds are expected throughout the weekend.

“It’s going to get worse before it gets better,” said Ken Pimlott, director of the California Department of Forestry and Fire Protection.

Authorities estimate at least 191,400 acres have burned so far, an area nearly the size of New York City.