Arson and bomb investigators were looking into what caused the devastating San Diego County wildfires, several of which burned close to roads, officials confirmed Thursday.
Several people were interviewed at the scene of the Lakeside fire near Aurora Drive when it started just after 5 p.m. Wednesday, said San Diego County Sheriff Bill Gore.
Authorities have urged the public to call local law enforcement if they see any suspicious activity. Gore said "nothing is too small" to report.
Escondido police briefly detained a man Thursday afternoon but released him.
The wildfires raging across Southern California have scorched more than 10,000 acres, with crews struggling to protect hundreds of homes from advancing flames.
At a news conference Thursday afternoon, officials said an 18-unit apartment complex in Carlsbad and at least seven houses had been destroyed in the more than half-dozen brush fires that have flared up in San Diego County since Wednesday.
San Diego County Supervisor Dianne Jacob urged residents to heed evacuation orders as they come.
"That's the No. 1 priority, is to save life and then to save property," she said.
Even though fire conditions had improved slightly, she said the county remained on high alert for "dramatic" flare-ups.
"We are not out of the woods yet," she said.
In San Marcos alone, the 800-acre Cocos fire was just 5% contained as firefighters increased their air attack. Officials said evacuation notices covering 13,000 homes and businesses in San Marcos had been issued. Meanwhile, hundreds of people were checked into shelters, waiting for word on the status their homes.
Rebecca Kuritz, 35, was at home with her 15-year-old son Wednesday afternoon when she realized there was a fire headed straight toward their San Marcos complex.
"People were running out of our complex," Kuritz said. "Running."
She grabbed her son and left with only one shoe on.
"I've lost enough stuff in my life, I just wanted to get out of there," Kuritz said. "It's just stressful. You realize what's really important really quick."
She recalled evacuating during three previous fires, including one in 2007 in which she lost her childhood home in San Marcos' Elfin Forest.
As of Thursday morning, three structures had been destroyed and an additional one damaged by the Cocos fire, which officials said had become their No. 1 priority.
Overnight, helicopters made 45 water drops, said San Marcos Fire Chief Brett Van Wey.
On Thursday, helicopter-borne crews were looking for hot spots and an additional 22 military aircraft were in the region providing additional support for the county, officials said.
"For fires like this, for lack of a better term, you call the world," said Robert Scott, San Marcos Fire division chief.
Inmate fire crews from the California Department of Corrections and Rehabilitation provided additional support along the fire lines, but officials said the scene was frantic.
"It's hectic," the agency's Lt. Keith Radey said. "That's why everybody's like scrambling."
The state's fire risk has been extremely high due to drought conditions and strong Santa Ana winds, Cal Fire spokesman Daniel Berlant said in a video address Thursday.
Firefighters responded to nearly three dozen fires Wednesday and are still battling eight active blazes in Southern California, seven of them in San Diego County, which combined have charred more than 10,000 acres, he said.
"Already this year, Cal Fire has responded to an over 100% increase in the number of wildfires than average," Berlant said.
The fires were more proof that California's drought conditions have created a year-round fire season.
"It starts with the drought," Berlant said. "The grass, the brush and the trees -- not only in San Diego County, really across California -- are really dry."
Fire crews can expect some short-term relief over the weekend, when a badly needed cool-down was expected to occur, forecasters said.