SAN FRANCISCO -- Officials have raised the number of homes and other buildings destroyed in this month's California wildfires to nearly 7,000 and said Thursday that the number will likely climb as crews continue assessing areas scorched by the blazes that killed at least 42 people.

The estimate of homes and structures burned is now at 6,900, up from 5,700, as fire crews returned to hard-hit neighborhoods and assessed remote and rural areas they could not get to earlier, said Daniel Berlant, a spokesman with the California Department of Forestry and Fire Protection.

He said most of the newly counted destroyed buildings burned on Oct. 8 and Oct. 9, shortly after the wildfires broke out in Northern California's wine country and other nearby areas.

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"The estimates are in structures and are mostly homes, but also includes commercial structures and outbuildings like barns and sheds," Berlant said.

Twenty-two of the 42 deaths in California's October fires happened in the Sonoma County wildfire, making it the third-deadliest in California history. A 1993 Los Angeles fire that killed 29 people was the deadliest single blaze, followed by a 1991 fire in Oakland that killed 25.

California Gov. Jerry Brown late Wednesday issued an executive order to facilitate recovery efforts as fire authorities say they've stopped the progress of wildfires.

Tens of thousands of people have been allowed back home but more than 15,000 people remain evacuated Thursday, down from a high of 100,000 last Saturday.

As the effort to rebuild from the wildfires gets underway, authorities have issued a warning about toxic materials in ash and debris, CBS San Francisco reports.

"I want to warn people that there are risks once we allow people back into areas where houses have burned to the ground," Santa Rosa Mayor Chris Coursey said Wednesday. "These are risks to your health and financial risks."

"There can be chemicals and asbestos and lead, plus plastic particles, all of that within that debris," Christine Sosko, Sonoma County's director of environmental health, told CBS San Francisco. "So we're very concerned about people rummaging kind of through that and disturbing it and then getting it to be airborne and inhaling that."

Sonoma County said it is working on a re-entry plan for homeowners to visit what is left of their properties. No cleanup work will start until sites have been declared safe and secure.

The U.S. Environmental Protection Agency will be managing the removal of toxic materials from thousands of fire-scorched properties.

Brown's order also allowed disrupted wineries to relocate tasting rooms and suspended state fees for mobile home parks and manufactured homes.

The order extends the state's prohibition on price gouging during emergencies until April 2018 and expedites hiring of personnel for emergency and recovery operations.

A number of fires have also been burning farther south. In Los Angeles County, authorities said a charred body was found on Mount Wilson, where crews were trying to surround a smoldering wildfire in steep terrain.

The male body discovered late Wednesday was recovered by the coroner's office, which will try to identify it, said Sheriff's Sgt. Vincent Plair.

California firefighters were also battling a blaze that sent smoke billowing into the college beach town of Santa Cruz, about 75 miles south of San Francisco.

The wildfire in steep and rugged terrain had grown to nearly half a square mile and the number of houses threatened by the fire had doubled to 300.

Several firefighters suffered minor injuries.