Los Angeles, California - A brush fire in a mountainous area north of Los Angeles triggered evacuations in two counties, scorching nearly 5,000 acres (2,000 hectares), authorities said Friday.

At least 10 zones in Los Angeles and Ventura counties were under evacuation orders, with 2,700 residents displaced as of 11 pm (0600 GMT) Thursday, Ventura County Fire Department spokesperson Andrew Dowd told AFP.

At least 400 personnel have been deployed to contain the fire, according to Dowd.

The blaze erupted as firefighters battled a separate wildfire – California's largest of the year so far – which raged for an eighth straight day and engulfed more than 99,000 acres in the Los Padres National Forest, threatening hundreds of homes.

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The latest fire has so far burned 4,856 acres and remains zero percent contained, Dowd said.

LA County Supervisor Kathryn Barger, who represents the area, urged residents to heed evacuation guidelines.

"The #CanyonFire is spreading fast under extreme heat & dry conditions near Ventura–LA County line," Barger wrote on X.

"If you're in Santa Clarita, Hasley Canyon, or Val Verde, take evacuation orders seriously – when first responders say GO, leave immediately. Keep aware--please don't risk lives."

The fires follow a July blaze that scorched more than 70,000 acres and needed hundreds of firefighters to contain it.

Fire authorities at the time noted that dry brush, sustained winds, and high temperatures were fueling the flames.

That came after several earlier fires, stoking fears of a difficult season in a state still reeling from wildfires that killed 30 people in January.