Orange County remained on high alert Tuesday as a pair of wind-driven wildfires continued their race toward populated areas, forcing 100,000 residents to evacuate and choking much of the region with smoke.

The larger of the blazes, the Silverado fire, broke out shortly after 6:45 a.m. Monday in the brush country around Santiago Canyon and Silverado Canyon roads. It had burned 12,535 acres by noon Tuesday. At least 90,000 residents were under evacuation orders, and the fire was 5% contained.

The cause of the blaze, which is burning on hilly terrain in state lands, is not clear. But in a report to the state Public Utilities Commission, Southern California Edison said it was investigating whether its electrical equipment might have caused the fire. The brief report said it appeared that a “lashing wire” may have struck a primary conductor and that an investigation was underway.

At least two firefighters working on hand crews were severely burned as they battled the flames, according to Orange County Fire Authority Chief Brian Fennessy.

The firefighters, ages 26 and 31, were both placed on ventilators after suffering second- and third-degree burns over half their bodies, Fennessy said.

“This is tough for me, tough for all my firefighters and certainly for the families of my two injured firefighters,” Fennessy said during a news conference outside the Orange County Global Medical Center, where the men were being treated.

“They’re gravely injured,” he said. “We’re doing all we can for them.”

There were no official updates on their conditions Tuesday morning, Capt. Thahn Nguyen of the fire authority said.

Nguyen said their injuries were “pretty severe,” and he could not say whether they were expected to make a full recovery.

Hours after the Silverado fire ignited, the Blue Ridge fire erupted in Santa Ana Canyon — a notorious wind tunnel said to have given the blustery Santa Anas their name.

The flames spread quickly as the fire pushed west toward Yorba Linda, threatening the town’s Hidden Hills community. By noon Tuesday, the blaze had engulfed 15,200 acres and was zero percent contained. At least 10,000 residents had been evacuated. Ten homes had been damaged and 2,500 were still threatened.

The two fires have spurred multiple evacuation orders and warnings. Residents can refer to the O.C. emergency public information map to check the status of their neighborhood.

“This is absolutely a large mutual aid fire, a lot of resources from all over the state,” Orange County Fire Authority Capt. Jason Fairchild said Tuesday, noting that more than 1,700 firefighters are battling the two blazes. “And we have additional resources coming in from farther away.”

Facing flames that could threaten multiple homes at once in the county’s suburban sprawl, firefighters have been relying on their engines’ 500-gallon tanks to beat back flames instead of connecting to hydrants so the crews aren’t “anchored down,” Fairchild said.

If the water supply were to become an issue, many of the engines are outfitted with pumps that would allow them to pull water from homeowners’ pools, he said.

Gov. Gavin Newsom on Tuesday said California had received a fire management assistance grant from the Federal Emergency Management Agency that will allow the state to receive 75% reimbursements for firefighting efforts related to the Silverado and Blue Ridge fires. The grant is provided through the president’s Disaster Relief Fund on cost-share basis.

“I want to thank FEMA and our partners at the federal level for their support,” he said.

Newsom said 42 fires had ignited across the state in the last 24 hours, many fueled by fierce winds. He thanked the California Department of Forestry and Fire Protection, along with local firefighting agencies, for their quick work in suppressing most of the blazes.

“We talk in historic terms,” he said, “and I remind you that six of the top 20 wildfires in our state’s history have occurred in 2020.”

More than 4 million acres have burned this year, and wildfires across the state have resulted in 31 fatalities, he said.

Monday’s dangerous winds — which saw gusts of up to 80 mph fueling the aggressive blazes — were expected to begin dissipating Tuesday afternoon, the National Weather Service said.

“They’re not going to be as strong as they were yesterday,” said Casey Oswant, a weather service meteorologist in San Diego.

Oswant said Tuesday’s gusts should peak around 30 mph and might start to spread moisture when they changed direction and flowed back onshore as the day went on.

A red flag warning will remain in effect in Orange County until 6 p.m., she said, and high wind warnings will expire at 2 p.m.

But people should not “completely relax,” as dryness is still a concern across the region.

“Definitely avoid burning if necessary, and if you see a fire, call the authorities,” Oswant said. “The threat is definitely still there, even though the winds are coming down.”

Monday’s combination of intense winds and low humidity were considered some of the most dangerous fire weather conditions of the year. The weather service reported gusts of 96 mph in the San Gabriel Mountains just south of Santa Clarita.

The winds also carried ash and soot left from the Bobcat fire earlier this month back into the skies, further choking Southern California with bad air.

By Tuesday morning, the government’s air quality monitoring agency had reported that Southern California had the worst air quality in the nation, with parts of Los Angeles and Orange counties and the city of Corona all hovering in the “unhealthy” range.

The South Coast Air Quality Management District issued a smoke advisory for Orange County through Tuesday. It also issued a windblown dust and ash advisory in Los Angeles, Orange, San Bernardino and Riverside counties, warning that hazardous particulate matter from wildfire burn areas may be spread through the air.

The windy conditions spurred Southern California Edison to warn customers in all of Los Angeles and Ventura counties, except for the Antelope Valley, that power could be shut off Monday to lower the chances of fires being sparked by downed power lines.

As of Tuesday morning, about 20,537 customers were without power, mostly in San Bernardino County. An additional 18,500 remained under consideration for a preemptive shutoff, according to Edison’s website.

The strong winds also hindered firefighting efforts Monday: Water-dropping aircraft had to be pulled off the Silverado blaze around 10:30 a.m. The aircraft remained grounded through the afternoon.

In Irvine, many parks remained closed. UC Irvine said Monday it was suspending campus operations through Tuesday.

Ash swirled and the stench of smoke hung in the air Tuesday as a light haze settled over southern Orange County.

Cars lined Glenn Ranch Road as riders paused to watch smoke billowing from a cluster of hills in the direction of Silverado Canyon Road. At least two firefighting planes circled the area. A firetruck blared its sirens down the hill.

Marc Church, 63, joined the row of passersby, snapping photos of the burning canyon. The smoke had lessened from the previous day, he said, motioning to the hills, where patches of charred black peeked through the brown haze.

Church lives in Mission Viejo, where he moved a year and a half ago from Irvine because his wife wanted to be closer to the hills. Now, they fear the wind could carry burning embers and ignite their backyard.

“It’s a risk whenever you move near these hills,” he said.

The family had packed a few boxes of important documents — car titles, birth certificates, bank information — and spent the morning gathering other necessities, including clothes, computers and chargers. They took shifts sleeping and keeping watch overnight, he said, and awoke to voluntary evacuations and the sounds of helicopters circling overhead.

“We didn’t get a lot of sleep,” Church said, adding that if the evacuation orders became mandatory, they would load up the car. “If we have to go, we’ll have to go.”

A similarly frightening scene had unfolded Monday, when trash cans and palm fronds were swept along empty streets in evacuated neighborhoods.

Lana Salameh, 45, had just dropped off her two youngest children at school and returned home in Irvine’s Eastwood community when she realized the sky was a dull orange. Trees were falling from heavy winds and smoke was seeping into the house, but she had not been informed that school was canceled.

She hustled back to Eastwood Elementary School to grab her 9-year-old daughter, Farah Abdelbari, whose tears were soaking her pink mask. She then picked up her 11-year-old son, Omar.

“They were scared. It wasn’t easy,” Salameh said. “My kids were crying, but we had to leave.”

They grabbed their passports and some bananas before arriving at an evacuation center set up at Quail Hill Community Center, which was reaching capacity.

Inside, about 30 people sat at socially distanced desks while small dogs were tied to table legs. Many were searching laptops for news reports of the fires. Salameh’s children got to work on school assignments.

Esther Lee, 55, and dozens of others waited in the parking lot for spots to open inside.

Hours before, Lee had been packing at her home in Lake Forest around 9:30 a.m. when she received a mandatory evacuation notice. Looking outside, she saw palm trees bending hard in the wind and smoke pouring down from the hill. She knew what she had to do.

Lee rushed to put important documents in her car and drove to a nearby park to coordinate with other family members.

“We didn’t have much time, and I didn’t want to stay too long,” Lee said. “We’re just staying put for now because the winds can be so unpredictable.”

Pat McGrath, 78, was making breakfast when a stranger pounded on her front door to inform her of the evacuation orders. The Irvine woman has no family on the West Coast.

“I just panicked. I started crying,” McGrath said. “I’m cold, I’m hungry, I’m stressed, and I don’t know what to do.”

Her voice was faint as she reclined into her seat at the Quail Hill Community Center with a beige cardigan draped over her.

“I was hoping there would be food or water, but I only got a bottle of water from a woman here earlier,” she said. “There’s a fountain down the hall, but I forgot my cane and my legs don’t work too well. I think your body doesn’t work as well when you’re stressed.”

Lorraine Elewaut’s firefighter brother called from Washington on Monday, when the Silverado fire burst into Irvine near the Elewauts’ Skyridge home.

“You need to have your emergency kit ready,” he admonished her.

His call, and the howling winds, kept the 67-year-old up all night while her husband, Bob, 75, slept soundly. In the morning, a call from the Orange County Fire Authority about voluntary evacuations prompted Elewaut to fly into action. She packed birth certificates, lease agreements and “of course, the photos.”

“It made me realize how little prepared I was,” she said.

Since the COVID-19 pandemic, the Elewauts have kept a robust store of supplies, but Lorraine said she found necessities scattered around the house.

Her brother called again Tuesday morning with another cautioning message, and a laugh: “Don’t forget to pack the alcohol.”

Adriana Cruz and her daughter Roxana, 11, had to evacuate their Yorba Linda home and stayed in a hotel Monday night. With the two of them, and their lumbering dog, Jacqs, penned up in a crate, the room proved to be crowded.

The Cruz family brought Jacqs to the OC Animal Care shelter in Tustin, which was welcoming evacuees’ small animals. Jacqs would stay Tuesday night while Cruz and her daughter waited to learn more about their neighborhood.

The whole process was “confusing,” Cruz said while wiping out the dog’s crate with a towel.

As for when the family could return home, Cruz shook her head.

“We don’t know.”