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The Airport Fire started around 1 p.m. Monday in the canyon and spread quickly in hazardous weather conditions, leading to the evacuation of more than 1,400 homes and triggering responses by more than 1,000 firefighters.
It started as county public works crews were trying to move boulders to prevent public access - mostly by motorcyclists - to an area of the canyon with a lot of dry vegetation that could ignite easily.
"The fire has been classified as unintentional," said Orange County Fire Authority Deputy Chief TJ McGovern.
"The cause of the fire was a spark from heavy equipment being used to replace barriers out there. Two employees from Orange County public works were utilizing heavy equipment to place large boulders as barriers on Trabuco Creek Road to restrict access into the vegetation."
"Out Trabuco Creek road, they were moving boulders to block access to the vegetation ... just doing barriers to keep people out of the vegetation because of the weather we have right now. The fuels are getting to that point. So we just don't want a lot of people in that vegetation unnecessarily."
As they were moving the boulders, they started seeing smoke emit from the loader basket. The workers attempted to use multiple extinguishers against the flame and called 911, he said.
But the flames spread quickly, amid an intense heat wave and shifting winds that have spread fires throughout the Southland over recent days. The blaze raged into the night, with AIR7 capturing flames near an antenna farm at Santiago Peak. It's unclear if there had been any damage.
The Airport Fire was estimated at about 5,432 acres just before 10 p.m., hours after it started on just a few acres of dry hillside brush.
Two firefighters were treated for heat-related injuries and one civilian was hospitalized for smoke inhalation. No significant property damage had been reported as of Monday evening.
A 3-year-old child and their parents were airlifted to safety, along with a man and his cats, according to the OCFA.
Residents of Robinson Ranch, Trabuco Highlands, the Trabuco Highland apartment complex and Meander Lane were ordered to evacuate. Sheriff's deputies were going door to door to issue and enforce the order.
Winds appeared to be blowing the fire away from Robinson Ranch.
Authorities were also advising voluntary evacuations for residents in the area of: Rose Canyon Road, Trabuco Creek Road, Trabuco Canyon Road, Trabuco Oaks Drive, Joplin Loop and Cook's Corner.
Nearby school districts were also announcing closures for Tuesday. Robinson and Trabuco elementary schools, under the Saddleback Valley Unified School District, were to be closed on Tuesday, including before and after school activities. The schools are expected to reopen Wednesday, depending on the progress of firefighting efforts.
Evacuation centers and pet reunion sites were being established.
A long-term care and reception shelter was established at Rancho Santa Margarita Bell Tour Regional Community Center, 22232 El Paseo in Rancho Santa Margarita.
A temporary evacuation site was established at the Lake Forest Sports Complex, 28000 Vista Terrace, Lake Forest.
A shelter for large animals was established at the Orange County Fair Grounds, 88 Fair Dr. in Costa Mesa.
Mission Viejo Animal Services established a meet and reunite area in the Ralphs parking lot at 31481 Santa Margarita Parkway to help residents reunite with pets. For help with a pet, call (949)470-3045 and press 2.
The fire was first reported around 1:30 p.m. when it was burning in an area described as Trabuco Creek Road near the remote-controlled airplane airport in Trabuco Canyon.
It was initially estimated at 7 acres but was spreading rapidly and by 3 p.m. had grown to around 292 acres - and then hit 1,860 by 4:30 p.m.
Evacuation details and emergency information for the Airport Fire is available from the Orange County Sheriff here.
Residents near Trabuco Canyon advised to evacuate as fire spreads quickly in dry brush
Winds were initially pushing the flames away from homes but authorities were taking precautions against a potential shift in wind direction.
Firefighters were attacking the blaze from the air and the ground, using handcrews, dozers, fixed-wing aircraft and helicopters, among other equipment.
The Trabuco Canyon blaze was one of multiple wildfires burning in Southern California at the tail end of an extreme heat wave that made for dangerous conditions. Winds were shifting flames in unpredictable directions while monsoonal moisture in the air was generating thunderstorms in some areas, leading to lightning strikes that had the potential to ignite new blazes.