TRABUCO CANYON (CNS) - Falling temperatures continued to provide a valuable boost to firefighters battling the Airport Fire burning in Orange and Riverside counties Thursday, with crews finally beginning to establish containment lines while again slowing the spread of the blaze.

As of Thursday morning, the fire was estimated at 23,410 acres, with 5% containment.

Orange County Fire Authority Capt. Steve Concialdi said about 770 firefighters were battling the blaze "and more are coming to assist."

"This marine layer and cooler temperatures along with the higher relative humidity are helping firefighters grow our containment fires and extinguish hot spots," Concialdi said Thursday morning. "Unfortunately, due to the marine layer helicopters were unable to fly last night, but starting this morning our firefighters are improving those containment lines and going into those burn areas and extinguishing hot spots."

As temperatures rise Thursday, "residents will see smoke," Concialdi said.

"We are constructing a large dozer containment line from below the fire, starting in Robinson Ranch and behind the communities of Dover Canyon and Coto de Caza all the way to Ortega Highway just in case we have any wind shift or if the Santa Ana winds develop at some point," Concialdi said. "This will be a barrier and will slow the fire and keep the fire away from those communities."

Crews were concentrating efforts on the fire's southeastern flank along Ortega Highway to ensure structure protection and douse hot spots, officials said.

At a Wednesday afternoon news conference, OCFA Division Chief Kevin Fetterman reported two civilian injuries -- one who suffered a medical emergency and one with unspecified burns -- and a total of 10 firefighter injuries.

Concialdi said earlier Wednesday most of those firefighter injuries were heat-related, "but one did get stung by numerous bees, and one sustained minor burns and the other couple had some injuries from fighting the fire, but all were released from the hospital and are doing well."

The end of the Southland's prolonged heat wave began assisting in the firefight Tuesday night, Concialdi said. Burn scars from the Holy Fire in 2018 and 2022 also provided much-needed breaks in the fuel feeding the blaze.

Structures have been damaged in both Orange and Riverside counties, although the exact number remained under assessment.

"We can confirm that there were some homes damaged and destroyed in the communities around Ortega Highway," but details were still being collected, Concialdi said.

As of Wednesday, the Orange County Fair and Event Center had taken in 93 horses evacuated due to the fire.

On Tuesday, the Orange County Board of Supervisors approved an emergency declaration in response to the fire, in hopes of obtaining additional financial resources for the firefight and eventual recovery. Meanwhile, Gov. Gavin Newsom secured assistance from the Federal Emergency Management Agency for all the fires in the state, including the Airport Fire, the Bridge Fire burning in Los Angeles and San Bernardino counties and the Line Fire in San Bernardino County.

The Airport Fire began about 1 p.m. Monday near Trabuco Canyon Road in the area of the remote-controlled airplane airport, said Orange County Fire Authority Capt. Sean Doran. By Tuesday morning, the fire had raced up the canyons and hillsides and crested into Riverside County, burning toward the El Cariso and Lake Elsinore areas, where evacuation warnings and orders were in place.

Ortega Highway was closed east of Quarry to Grand Avenue in Lake Elsinore. That area had been under a voluntary evacuation warning, but late Tuesday morning, mandatory evacuation orders were issued for areas along the highway near Caspers Park.

There were other roads were closed near the fire:

-- Plano Trabuco / Joshua Drive

-- Santa Margarita Parkway / Antonio Parkway

-- Plano Trabuco / Robinson Ranch

-- Avenida Empressa / Santa Margarita Parkway

-- Antonio Parkway / Alas de Paz

-- Trabuco Canyon / Trabuco Creek

-- Santiago Canyon Road

-- Live Oak Canyon Road

A mandatory evacuation order was previously issued for the Robinson Ranch community in Rancho Santa Margarita. Voluntary evacuation warnings were in place for residents on Rose Canyon Road, Trabuco Creek Road, Trabuco Canyon Road, Trabuco Oaks Drive, Joplin Loop and Cook's Corner. Evacuation warnings were issued Tuesday for Silverado and Modjeska canyons.

A care and reception shelter for evacuees was established at the Rancho Santa Margarita Bell Tour Regional Community Center, 22232 El Paseo. Large animals can be sheltered at the Orange County Fair Grounds, 88 Fair Drive in Costa Mesa.

Some pets were being sheltered at OC Animal Care at 1630 Victory Road in Tustin, officials said. Mission Viejo Animal Services was also helping residents with shelter for pets.

Additional evacuation warnings were also in effect for a host of Riverside County areas near the fire zone, generally in an area east of the Orange County line, north of the San Diego County line, south of Bedford Motor Way and west of Interstate 15.

Early Tuesday afternoon, some of those warnings became evacuation orders, impacting an area generally north of the San Diego County line, east of the Orange County line, south of Lake Elsinore near the base of Ortega Highway and west of South Main Divide Road/Grand Avenue.

An evacuation center was established at Santiago High School, 1395 E. Foothill Parkway, Corona. Large animals can be taken to the Jurupa Valley Animal Shelter, 6851 Van Buren Blvd., according to the Riverside County Fire Department.

Other evacuation centers are at:

-- Temescal Canyon High School: 28755 El Toro Road, Lake Elsinore.

-- Santiago High School: 1395 E Foothill Pkwy, Corona.

An evacuation shelter is open at Temescal Canyon High School in the big gym. The site is equipped with cots, air conditioning, Wi-Fi, water, snacks, and welcoming staff.

Animal shelters are at Jurupa Valley Animal Shelter: 6851 Van Buren Blvd, Jurupa Valley.

Large animal shelters are at:

-- Los Alamitos Race Course, 4961 Katella Avenue, Cypress.

-- Nohl Ranch Saddle Club: 6352 E. Nohl Ranch Rd. Anaheim.

Mission Viejo Animal Services is at the Bell Tower Regional Community Center to assist with sheltering pets and help evacuated residents reunite with their pets. Those who need assistance with pets, can call 949-470-3045 and press 2.

An additional Large Animal Shelter is available at the Murrieta Equestrian Center located at 42670 Juniper St, Murrieta. Basic food and water are available at animal shelters. Riverside County residents needing assistance with large animal evacuations can call 951-358-7387.

Fire crews on Wednesday deployed additional resources into the El Cariso area in Riverside County southwest of Lake Elsinore in hopes of shoring up structure protection and hoping to make a stand against the fire's advance.

Talbot Hayes of the Cleveland National Forest said the fire was being driven by weather, fuel and topography. Firefighters were working in areas with grass as high as 4 feet with chaparral as high as 8 feet, Hayes said. The terrain is at times "barely hikeable even for our most fit firefighters."

There were 36 cabins in Trabuco and Silverado canyons that firefighters had yet to assess for damage, he said.

Orange County Fire Authority Deputy Chief TJ McGovern told reporters Monday night that the fire was accidentally sparked by a county work crew. McGovern said Orange County Public Works crews were working in the area near Trabuco Creek Road, using heavy equipment to place boulders meant to replace barriers used to restrict access to the vegetation.

The OCFA was using new firefighting helicopters that can dump 1,000 gallons of water on the flames, Doran said.

The Corona-Norco Unified School District opted to close Wilson, Temescal Valley and Todd elementary schools in the Corona-Norco Unified School District have been closed since Tuesday due to the proximity of the fire and the resulting poor air quality, and all three will remain closed for the rest of the week, according to the district. All schools in the Lake Elsinore Unified School District were also closed Tuesday and Wednesday.

Robinson and Trabuco Elementary schools in the Saddleback Valley Unified School District in Orange County were also closed Tuesday and Wednesday, and remained closed Thursday. Santa Margarita Catholic High School reopened Thursday on a limited schedule, but will close again Friday for a previously scheduled teacher convocation event.

Later, with Mo'Kelly