Crews in Southern California tamed some of the wildfires burning across San Diego County, thanks to cooler temperatures and calmer winds Friday. But the blazes still posed threats to residents and structures.
A 57-year-old man pleaded not guilty to an arson charge that accuses him of having tried to add fuel to one of the fires and was held on $75,000 bail, authorities said Friday.
The man, identified as Alberto Serrato, was seen adding brush to a fire in the San Luis River bed, San Diego County District Attorney Bonnie Dumanis said at a news conference. If convicted, Serrato could face seven years in prison.
On Thursday, two people were arrested in the Escondido area on suspicion of attempted arson. Isaiah David Silver, 19, was held on $50,000 bail; details about the second person were withheld because, at age 17, he or she is a juvenile.
The newest fire, one of three in the area around Marine Corps' Camp Pendleton, forced new evacuations Friday as it grew to 800 acres.
A second fire nearby grew on Friday to more than 15,000 acres but was 40 percent contained, according to the base.
In all, three sections within the vast base were evacuated — camps Las Flores, Pulgas and Margarita — a spokeswoman told NBC News. A firefighter working to expel the flames was hospitalized for heat exhaustion as the blazes left charred hillsides, homes and vehicles in their wake.
The injured firefighter was from Camp Pendleton, a major Marine base in San Diego County roughly the size of Rhode Island, officials said.
He received treatment for heat exhaustion, but no further details were released about his condition or identity.
A third fire on the base — dubbed the Tomahawk fire — was 65 percent contained Friday evening and had burned more than 6,500 acres, the base reported.
All non-essential personnel on the base were sent home at noon, according to the camp's public affairs office.
On Thursday, the fires claimed their first known victim when a badly burned body was found in a transient encampment near Carlsbad, according to local officials.
Some of the fires rampaging through the region had showed signs of abating early Thursday, before the Cocos fire showed "explosive growth" in the San Marcos area and headed toward the city of Escondido, said Capt. Mike Mohler of the California Department of Forestry and Fire Protection, or Cal Fire.
Explosions could be heard when a number of buildings were engulfed in flames and black plumes of smoke filled the sky, as the fire ate up hillsides and destroyed eucalyptus trees. Visibility was reduced to a few feet in the worst-affected parts.
The blaze, dubbed the Cocos fire, was 30 percent contained Friday afternoon, and some residents in the San Marcos area were allowed back into their homes, San Marcos officials said. Meanwhile, residents in at least five neighborhoods were warned not to return to their houses.
"Please evacuate," San Diego County Sheriff Bill Gore urged residents. "There will be no vandalism. We want you to return safely and not get hurt in these fires."
"The grass out there is nothing but kindling for these fires,” Gore said.
By Friday evening, the Cocos fire had scorched about 2,520 acres and was burning close to Cal State University-San Marcos, according to NBC San Diego. The college evacuated Wednesday and remained closed Friday, according to the school’s website.
Twenty homes have been destroyed in that fire, along with an 18-unit apartment building and two commercial buildings. Another apartment building suffered considerable damage, San Diego County said in a damage assessment.
Also the Harmony Grove spiritualist retreat, a century-old spiritual center west of Escondido lost more than half of its buildings, NBC San Diego reported.
The first fire that flared in the area was ruled an accident Friday, Cal Fire spokeswoman Lynne Tolmachoff said. That blaze in Rancho Bernardo was caused by sparks from faulty construction equipment, she said.
The cause of 10 other fires that started in the region between Tuesday and Thursday has not yet been determined, and the outbreak has caused officials to question whether some were triggered deliberately. The true extent of the damage will not be known for days.
Santa Ana winds and unseasonably high temperatures have contributed to the devastation as mercury readings rose above 100 degrees this week.
Some cooling and higher humidity was expected on Saturday and Sunday, according to the National Weather Service. But the area was to remain under a red flag warning until midnight Friday, the weather service said.
Tens of thousands of people have fled their homes north of San Diego, schools have been closed, graduation ceremonies have been canceled and amusement parks, including Legoland, have been shuttered.
The worst fire in California's recent history occurred in central San Diego County in 2003, when more than 437 square miles were scorched, nearly 3,000 buildings were destroyed and 15 people were killed.
M. Alex Johnson of NBC News and The Associated Press contributed to this report.