A fresh spate of Southern California wildfires roared to life on Thursday, destroying homes and forcing evacuations, as the region faced a second day of explosively fierce Santa Ana winds that have fanned flames, displacing thousands of residents.

The most destructive among several new wind-driven blazes in the region erupted hours before dawn on the rugged slopes of the San Bernardino National Forest above the city of San Bernardino, barreling downhill into the north end of town.

The so-called Hillside fire quickly devoured more than 200 acres (80 hectares) of dry scrub and destroyed or damaged at least six homes before firefighters managed to keep the flames from advancing farther, fire officials said.

As of early afternoon, crews had managed to carve containment lines around 50% of the fire’s perimeter. No injuries were reported, but evacuation orders remained in effect for nearly 500 homes, displacing about 1,300 residents.

The cause of the blaze is still under investigation. The San Bernardino County Fire Department said on Twitter that no power lines were located where it had originated.

The latest recurrence of Santa Ana winds, howling into the region through mountain passes from the desert, coincided with extremely low relative humidity and a prolonged lack of rainfall that has left vegetation tinder-dry across the region.

Those conditions prompted the National Weather Service to create a new alert level, issuing an “extreme red-flag warning” for fire danger in Los Angeles and Ventura counties.

Winds were beginning to subside on Thursday, though red-flag warnings were extended through Friday evening in mountain and foothill areas deemed especially susceptible to high gusts.