BANNING, Calif. (AP) — Thousands of people were under evacuation orders today after a wildfire in mountains east of Los Angeles exploded in size as crews battled the flames in triple-digit heat.

The blaze straddling Riverside and San Bernardino counties consumed more than 23 square miles of dry brush and timber, according to the California Department of Forestry and Fire Protection.

There was zero containment early today. The cause is under investigation.

The blaze began as two adjacent fires reported Friday evening in Cherry Valley, an unincorporated area near the city of Beaumont about 85 miles east of downtown Los Angeles.

Flames leapt along brushy ridge tops and came close to homes while firefighters attacked it from the ground and air.

One home and two outbuildings were destroyed, Cal Fire said. No injuries were reported.

Evacuation orders and advisories were issued for mountain, canyon and foothill neighborhoods. Campgrounds and hiking trails were closed in the San Gorgonio Wilderness area of the San Bernardino National Forest.

A huge smoke plume was visible for miles around and contributed to poor air quality.

The mercury hit 105 degrees Saturday in nearby Palm Springs. The National Weather Service said “dangerously hot conditions” were expected to continue because of high pressure over much of Southern California.