Authorities in Southern California attempted to gain control Friday over a fast-moving wildfire that torched dozens of homes and businesses, shuttered schools and forced over 10,000 people to evacuate.

Fueled by strong wind gusts, the so-called Mountain Fire exploded in size after it was first reported Wednesday morning in Somis, an unincorporated community in Ventura County. Inspection teams reported the fire destroyed at least 132 structures, mostly homes, and damaged 88 others as it spread to more populous neighborhoods northwest of Malibu and Los Angeles.

As of Friday morning, the fire had engulfed 20,596 acres and was 7% contained, according to the the state's wildfire-fighting agency, Cal Fire. Dozens of schools and colleges canceled classes on Thursday and Friday as the fire knocked out power and triggered nearly two dozen road closures.

A northern section of the blaze, near the city of Santa Paula, burned in steep, rugged terrain, hampering firefighters efforts to quell the flames. Crews also grappled with low pressure as the expansive emergency effort overwhelmed the local water system.

Ventura County Sheriff Jim Fryhoff said at a news conference that 10 people were injured, including several from smoke inhalation; none of the injuries appeared to be life-threatening. A firefighter was among the victims, according to Cal Fire.

Fryhoff said 400 homes were evacuated on Thursday and 250 residents decided to stay despite evacuation orders, which were active across 12 zones and affected the Camarillo, Ventura, Santa Paula and Fillmore areas. About 800 homes were empty when emergency responders arrived to warn people about the danger.

"The devastation is absolutely heartbreaking," Fryhoff said.

Mountain Fire triggers flurry of school closures

A number of Ventura County school districts and colleges closed as the Mountain Fire continued to rage and disrupt the lives of thousands of residents.

Among the closures on Thursday and Friday were Oxnard College, Moorpark College and Ventura College as well as dozens of county school districts. The individual schools under evacuation orders serve well over 70,000 students, according to a list compiled by the Ventura County Office of Education.

When the fire erupted early Wednesday morning, several schools were in session and had to evacuate.

Students, faculty and staff of Camarillo Heights Elementary School had to flee, according to a statement from the Pleasant Valley School District. Oxnard Union High School District closed down eight high schools and transported students from one school to another to be picked up.

Jesus Vaca, principal of Somis School, said the 219-student campus was in the "lucky part of town" and didn't have to evacuate. However, some students stayed on campus after the school day was over because their family homes are within the evacuation zone.

– Isaiah Murtaugh, Ventura County Star

Mountain Fire overwhelms water system, hampers operations

In addition to the rugged terrain, weak water pressure became an obstacle for fire crews attempting to gain a foothold and halt the fire's spread.

Officials said the water system was being used to fill hundreds of engines and that every fire hydrant was being tapped. "There was so much firefighter demand for (fire) suppression that it overwhelmed the system," said Ian Prichard, deputy general manager for the Calleguas Municipal Water District, which provides water to roughly three quarters of Ventura County residents.

Firefighters adapted. They went to lower elevations, filled up water tankers and brought that supply to the engines in the hills, Prichard said. However, power outages also hampered their efforts, forcing the use of portable generators. The fire also burned a water pumping station.

Fire crews plan to take advantage of the cooler temperatures and lower winds at night by flying helicopters and dropping fire-retardant chemicals, Ventura County Fire Chief Dustin Gardner said at a news conference Thursday. He said he expects crews will spend "the next four or five days getting this under control."

– Tony Biasotti and Tom Kiske Ventura County Star

Gov. Gavin Newsom signs emergency declaration in Ventura County

California Gov. Gavin Newsom on Thursday announced a state of emergency in Ventura County and said he secured a grant from the Federal Emergency Management Agency to "help ensure the availability of vital resources to suppress the fire," his office said in a statement.

Newsom said 3,500 homes structures and businesses were threatened by the wildfire. In response to the Mountain Fire and other blazes across the state, the governor positioned 48 pieces of firefighting equipment, nine helicopters and over 100 personnel throughout 19 counties since Sunday.

“This is a dangerous fire that’s spreading quickly and threatening lives. State resources have been mobilized to protect communities, and this federal support from the Biden-Harris Administration will give state and local firefighters the resources they need to save lives and property as they continue battling this aggressive fire," Newsom said.

As of early Friday, over 2,400 personnel have been assigned to Mountain Fire in a large containment effort involving 378 fire engines, 14 helicopters and 17 bulldozers, according to Cal Fire.

Red flag warnings active in Southern California

While red flag warnings in Ventura County expired, the advisories urging people not to burn anything outdoors were in place throughout other parts of Southern California.

Areas under red flag warnings are experiencing "critical fire weather," meaning there's a combination of strong winds, low humidity and warm temperatures that can fuel "extreme fire behavior."

The National Weather Service office in San Diego issued a red flag warning for parts of San Bernardino and Riverside counties, citing danger posed by northeast winds and humidity levels of 5 to 10%.

"Any fires that develop will likely spread rapidly," the weather service warned. "Outdoor burning is not recommended."

Contributing: Jeanine Santucci and Jorge L. Ortiz, USA TODAY

(This story was updated to add new information.)