CARLSBAD, California (CNN) -- A major firefighting offensive Thursday sought to douse wildfires that have so far charred 9,987 acres in California's San Diego County, with the worst being a nearly uncontrollable blaze in San Marcos.
Helicopters, military aircraft and extra crews, worked the fire, which fire officials said was only 5% contained as it burned 800 acres Thursday morning in San Marcos, home to a California State University campus and a heavily populated area.
The biggest fire -- at 6,000 acres on the Marines Corps' Camp Pendleton -- was only 20% contained, the military base said Thursday. Much of the land on the base is open acreage used for training exercises.
In broad daylight at noon, the fire blackened the skies in one San Marcos neighborhood and sent a "firenado" -- a column resembling a tornado with smoke and flames shooting from it -- rising and twisting into the air. The overall blaze forced the university to cancel this week's commencement and other activities, officials said.
In all, firefighters faced three dozen fires overnight, but as of mid-morning Thursday, that number had been reduced to eight, Cal Fire spokesman Daniel Berlant said.
In Carlsbad, where a fire prompted 23,000 evacuation notices Wednesday, Mayor Matt Hall declined to address some residents' speculation whether arson was behind so many fires in the county.
"I'm sure people are thinking about that," Hall said. "I would just ask people to keep on what we're having to deal with today."
Hall hoped evacuated residents could return to their homes on Thursday, but that decision depends on how the hot and dry Santa Ana winds blow during the day, he said.
"I know everybody's anxious to get back in their home," Hall said.
County residents who lost their homes to fire will be eligible for tax relief, county officials said.
San Marcos evacuates
Evacuation orders for several neighborhoods in San Marcos remained in place Thursday and at least 350 evacuees without alternate housing spent Wednesday night in shelters, officials said. Schools in many areas of the county were shut down because of the fire, including the San Diego Unified School District.
With sunrise Thursday, firefighters knew they were in for a long day.
"As quickly as the sun came up, so did the smoke," and the smoke meant fire, said Cal Fire Battalion Chief Nick Schuler.
In addition to high temperatures, dry winds and low humidity, officials were concerned about firefighter fatigue after two days of battling the blazes.
In fact, Thursday will be the hottest day of the week, according to the National Weather Service, with forecast highs between 98 and 106.
The cause of the numerous wildfires remained under investigation Thursday, but San Diego County Sheriff Bill Gore noted the tinderbox conditions of southern California. Grasses were so dry that setting a fire would take only a few hundred degrees, and a spark from a catalytic converter easily carries 2,500 to 3,000 degrees of heat, Gore said.
"The grass is nothing but kindling for these fires," he told reporters.
Working in firefighters' favor Thursday were calmer Santa Ana winds -- the dry, hot gusts originating from the desert.
"We're fortunate today not to have the winds we had," said San Marcos Fire Chief Brett Van Wey.
About 2,200 homes in San Diego County were without power, officials said.
As homeowners seek to repair their homes or find alternative housing, Sheriff Gore said authorities will be watching for vandalism and price gouging at motels and hardware stores. Prosecutors will file charges against anybody taking advantage of homeowners' tragedies, Gore said.
San Diego County Supervisor Dianne Jacob said additional air tankers and firefighting helicopters will join the effort.
Firefighters deployed across the county, jumping on every hotspot that flared up.
The region is bone dry after months of little rainfall and temperatures are brutally hot, especially for May. Wildfire season typically peaks over the summer and into the fall.
"The common theme statewide this year is unprecedented number of fires and fire activity across the state, in many cases two to three months earlier than normal," Ken Pimlott, director of the California Department of Forestry and Fire Protection, told CNN's "New Day."
Getting the word out
Alert San Diego, a countywide notification system, sent out nearly 122,000 emergency telephone notifications on Wednesday as the wildfires sprang up.
Carlsbad Fire Chief Michael Davis said that as of Thursday, the Poinsettia Fire in Carlsbad has burned 400 acres and is 60% contained. Four homes and 18 units of an apartment building were destroyed by the fire, he said.
Sophie Payne of Carlsbad lost her hilltop house in the fire. Only a stone entrance at her front door and several walls remained standing Thursday, as her family dug through the rubble.
"This is my dream house, and what can I say," she said, looking at the destruction.
They found some family keepsakes in a small safe, and while intact, the papers were charred at the edges. "It's just falling apart," Payne said.
In the distant horizon, Payne could see the newest fire consume parts of San Marcos. In her 42 years living in Southern California, she's "never, never, never" witnessed so many wildfires at one time.
Numerous roads have been shut down while others have become clogged with people trying to escape.
Christina Echols of Oceanside hasn't been told to leave -- yet. But with her home sitting "in the middle of three fires" and a little over 7 miles from the San Onofre nuclear power plant, she knows that call could come at any moment.
"I am afraid of the fires right now," Echols told CNN's Erin Burnett.
She has plenty of company. Zeb Navarro, a CNN iReporter, said students at Palomar College in San Marcos are on pins and needles.
The school canceled activities Wednesday night, though Thursday classes are still on.
"Students are scared, and several of them are leaving," Navarro said. "Everyone is worried and praying that all is safe."
Military facilities threatened
Another fire ignited around Camp Pendleton, a mammoth Marine base and training facility for multiple military branches, prompting evacuations of the O'Neill Heights Housing Community, the De Luz Child Development Center and Mary Fay Pendleton Elementary School, the Marines said.
Another blaze burned in the community of Fallbrook, adjacent to the military post, which is the West Coast boot camp for enlistees.
Cal Fire said the wildfire charred 6,000 acres around the military facilities.
Only 20% of the blaze, called the Tomahawk Fire, was contained, the Marine base said Thursday.
A precautionary evacuation was ordered at the nearby San Onofre nuclear power plant, which has been offline for two years because of another wildfire. Southern California Edison spokeswoman Maureen Brown said "there is no safety threat," though.
Among other locales, fires prompted the evacuations of the Legoland amusement park in Carlsbad on Wednesday, though it reopened Thursday.
Witness describes blaze as 'incredible'
The ferocious fires made for sensational viewing.
"Oh, my God! Oh, my gosh!" California resident Kristin Michalec said on a video she shared with CNN as she drove through raging flames in Carlsbad, near where she lives.
"It was so hard to see because of the thick smoke," she later told CNN in an interview.
Rich Breeze saw a burning house explode in Carlsbad.
"No one hurt that I know of. Everyone was out of the house at the time," Breeze told CNN iReport. "We were just right there when it exploded. It was just super intense.
"The fire was just incredible. It was beyond anything you've ever seen before," he said.
Jay Ringgold, an information technology manager in Carlsbad, smelled the smoke easily. Santa Ana winds, also called devil winds, whipped up the fires.
"People were very surprised that it came that close to the business district. There are a lot of big companies there -- near that is a brush area and homes," said Ringgold, a CNN iReporter. "Everyone was panicking and wanting to get out of there."
CNN's Dan Simon reported from Carlsbad, while Ed Payne wrote from Atlanta. CNN's Greg Botelho, Michael Martinez, Amanda Watts and AnneClaire Stapleton contributed to this report.
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Posted by: Nick Viviani