BONSALL, Calif. -- Crews took advantage of calm wind conditions and worked through the night to cut containment lines around the dormant Lilac Fire in northern San Diego County, but officials said they don't expect full containment until Dec. 21 .
As of 7 a.m. Saturday, the fire was 20 percent contained, according to Cal Fire, the state agency coordinating the fire fight. The fire had burned 4,100 acres, a figure that has not changed since Thursday night. The fire destroyed at least 105 structures and damaged another 15. At least six people were injured in the fire, but no one has died.
Although the fire has not grown in size, there remained many smoldering and actively burning hot spots inside the fire perimeter. Winds were expected to pick up again on Saturday and Sunday, increasing the danger that wind-born embers could spread the fire.
"Just because we're not seeing smoke in the air doesn't mean that we've turned the corner on this fire,'' Chief Ken Pimlott, director of Cal Fire, said early Friday afternoon.
The fire continued to threaten about 1,500 buildings, Cal Fire said. At the peak of the disaster, about 20,000 people were forced to evacuate their homes, but many were allowed to return Thursday night. On Saturday, about 10,000 people remained evacuated.
"There's still tons and tons of hot spots out there," Cal Fire Capt. Jon Heggie said.
Crews have largely transitioned their efforts from the air to the ground, he said. More than 800 firefighters and 103 fire engines were assigned to the fire. They were using six bulldozers, eight water tenders and four helicopters to put out hot spots and extend containment lines around the perimeter of the fire.
Strong winds are expected to return Saturday afternoon and continue into Sunday.
A "red flag" warning issued by the National Weather Service is in effect until 8 p.m. Sunday. The strongest winds are expected in the San Diego County mountains and foothills, with gusts over 60 mph, accord to the NWS.
The winds, coupled with humidity levels below 15 percent, make for prime fire conditions.
"Winds will diminish steadily from Sunday afternoon through Sunday night, and the critical fire weather conditions will wane Sunday night," the NWS said. "However, offshore flow will prevail through next week and continue very low humidity and occasional local gusty winds, though current indications are that we will have elevated versus critical fire weather conditions most of the week."
People should avoid activities that could cause fires, authorities said. That includes keeping vehicles off dry grass, practicing safe towing, avoiding activities with open flames, properly discarding cigarettes and obeying burn bans.
Gov. Jerry Brown issued a state emergency proclamation for San Diego County and Friday morning President Donald Trump approved an emergency declaration for the state due to the Lilac Fire and other large fires burning in Ventura and Los Angeles counties.
After breaking out Thursday, the flames moved quickly as the blaze grew to 50 acres as ground and airborne crews labored to keep the blaze from becoming an out-of-control conflagration like others raging this week across Southern California.
The cause of the blaze -- which broke out amid a National Weather Service "red flag" wildfire warning slated to expire Sunday night -- was not immediately clear.