The Thomas fire, which has burned through Ventura County for more than a week and entered Santa Barbara County over the weekend, has now scorched 237,500 acres and is 25% contained, fire officials said Wednesday.
The fire, which ignited Dec. 4, grew by 1,500 acres overnight, a Ventura County Fire Department public information officer tweeted Wednesday.
"Firefighters made good progress overnight," the public information officer account tweeted. "Thomas is moving North and West toward the Santa Ynez mountain range away [from] populated areas."
On Tuesday evening, authorities said they had "turned a corner" in fighting the blaze along its eastern flank in Ventura County. Winds were relatively calm and evacuations were lifted in the Lake Casitas area. However, officials warned stronger winds could return Thursday or Friday.
On the Santa Barbara County side, the fire continues to threaten the communities of Santa Barbara, Carpinteria, Summerland, Montecito and surrounding areas. The tedious, but vital, work of clearing brush down to the dirt as a fire barrier in the hills above Santa Barbara County's wealthy beach enclave will continue Wednesday.
More than five miles of additional containment line needs to be created by hand above Montecito and its neighboring communities as the Thomas fire continues its slow march west toward the Santa Ynez range, officials said.
About 600 fire engines are jammed into the narrow, winding roads in the Santa Barbara County foothills. Trucks are spraying retardant on grassy hillsides and firefighters are wrapping indefensible, small buildings in protective metallic sheeting that looks like tinfoil to reduce the chances they ignite.
Firefighters used a similar strategy to protect historic sequoias from the Rough fire in 2015.
Deeper in the forest above Santa Barbara near Gibraltar Dam, crews have worked day and night building a defense to stop it from reaching the Santa Ynez mountains.
"We want to stop it in its tracks," said Charles Esseling, a public information officer from the California Department of Forestry and Fire Protection in Riverside County.
The fire's spread northwest has also been slowed because its reached the burn scar from the massive Zaca fire of 2007.
Firefighters are attacking the flames directly by air and ground south of Highway 33 while containment lines are constructed, Esseling said.
With containment lines safely protecting Ventura and Santa Paula to the east, firefighters there will be on a "seek and destroy" mission for any lingering hot spots that could threaten precious avocado groves, fire officials said at a morning briefing at the Ventura County Fairgrounds.
"This fire is a beast and you're gonna kill it," Martin Johnson, Santa Barbara County fire division chief, told fire crews. "I have no doubt."
As firefighters continue to gain a handle on the fire — which is the fifth-largest in state history — California fire officials offered a hint as to what may have ignited the Thomas and other destructive blazes that tore across Southern California last week.
It likely will take months for fire officials to determine the cause of the fires, but state officials have notified Southern California Edison that the utility's equipment is under investigation. Power lines downed by high winds have been the cause of major brush fires in the past. The far smaller Skirball fire in Los Angeles was started by a cooking fire at a homeless encampment, officials said this week. But investigations into other fires are expanding, according to SCE.
"The investigations now include locations beyond those identified last week as the apparent origin of these fires," the power company said in a statement. "SCE believes the investigations now include the possible role of its facilities."
As a precaution last week, the utility shut off power temporarily to parts of Riverside County during high winds.
As of Tuesday, Edison said it was finishing restoring equipment damaged in the Liberty, Rye and Creek fires — replacing more than 300 poles with 200 more waiting.
Times staff writer Brittny Mejia contributed to this story.