Active flames were visible amid relatively calm winds Monday morning on a ridgeline above Carpinteria, one of several communities threatened by the wildfire, which was 20 percent contained.
The 231,700-acre blaze is the fifth-largest in California's history. The 2003 Cedar Fire, the state's biggest brush fire on record, burned 273,246 acres in San Diego County, according to Cal Fire.
MORE: List of evacuations, school and road closures caused by Thomas Fire
In the Montecito area, several multimillion-dollar homes were among the 18,000 structures threatened by the Thomas Fire.
Since the evening of Dec. 4, when the inferno erupted in Santa Paula, it has destroyed 868 structures, most of which were single-family homes. Officials said Monday that 525 homes were destroyed in the city of Ventura, while 138 were damaged.
In unincorporated areas of Ventura County, 342 structures were destroyed and 49 were damaged. One home was destroyed in an unincorporated part of Santa Barbara County.
The damage caused also means the Thomas Fire is among the top 10 most destructive wildfires in the state's history, according to Cal Fire.
Mandatory evacuation orders remained in place for parts of Ojai, Casitas Springs, Matilija Canyon, Carpinteria and Montecito.
By Monday afternoon, all mandatory and voluntary evacuation orders were lifted for Ventura, with the exception of areas north of Foothill Road from Day Road to Kimball Road.
PHOTOS: Thomas Fire devastates Ventura County
Schools in parts of Santa Barbara County were closed as the fire raged on in the foothills. Parts of the fire were burning in inaccessible spots, which meant only air tankers and helicopters could do the work.
Capt. Steve Concialdi said about 1.7 million gallons of water has been dropped by aircraft since the Thomas Fire started last week.
A 70-year-old Santa Paula woman was killed in a car crash on an evacuation route in Wheeler Canyon on Wednesday, the Ventura County coroner said. No other fire-related fatalaities or major injuries have been reported.
Firefighters from 856 engine companies were involved in the firefight, whose cost has reached $38.37 million, according to Cal Fire. Twenty-seven water-dropping helicopters and 48 water tenders were also in the burn area Monday morning.
The cause of the blaze is under investigation.