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FRAZIER PARK, Calif. (KTLA) — Hundreds of firefighters continued to battle a brush fire on Thursday that had burned over 3,500 acres in the Frazier Park area.

The blaze, dubbed the ‘Grand Fire,’ was just 15 percent contained, fire officials said. More than 600 firefighters were on the lines.

Fire crews took advantage of a break from the wind Wednesday night, which had fanned the flames earlier in the day.

They used bulldozers to build up containment lines and clear brush, said Sean Collins, spokesman for the Kern County Fire Department.

The most active front was in Ventura County, where the fire had spread and was burning through brush in the Los Padres National Forest, fire officials said.

The fire broke out around 1:20 p.m. Wednesday near Frazier Mountain Park Road and Grand Terrace Drive, not far from unincorporated Frazier Park.

“I could see the planes and the helicopters right away,” said resident Kayvon Bakitar.

He was at his office in Frazier Park when he saw the smoke. He rushed back to his home, nestled in the mountains on Grand Terrace State Drive.

Within about 20 minutes, the flames had advanced considerably, he said.

“They didn’t ask us to leave, but they did ask us to basically be prepared,” Bakitar said.

Firefighters on the ground from Los Angeles, Kern and Ventura counties worked to build a line around the fire and protect structures.

They were aided by seven air tankers and four water-dropping helicopters.

The air attack was suspended at nightfall, but it was expected to resume again on Thursday morning.

Mandatory evacuations were ordered for Hungry Valley Park and Piru Creek Campground as the flames spread. Those areas remained closed on Thursday.

Deputies had planned to evacuate Frazier Mountain High School, but students had already left for the day, according to the Kern County Sheriff’s Department.

The school was closed on Thursday because of the fire. Frazier Park School, Pine Mountain Learning Center and El Tejon School were all expected to be open.