Updated

A wildfire threatening homes in Southern California's rugged San Bernardino Mountains grew to over 12 square miles Tuesday while authorities reopened Highway 1 on the state's central coast after parts were closed due to the huge wildfire just north of Big Sur.

Mandatory and voluntary evacuations covered 5,300 homes in the Southern California fire area between mountain communities around Lake Arrowhead and the high desert city of Hesperia to the north, said Lyn Sieliet, a U.S. Forest Service spokeswoman. The number of people who left was not known.

Southwest winds pushed the fire northward through the mountains toward the desert.

Schools in Hesperia were closed as a precaution because of the fire's movement and two neighboring districts also shut down for the day due to poor air quality caused by smoke.

More than 900 firefighters aided by retardant-dropping air tankers and water-dropping helicopters had just 6 percent of the fire contained, but no structures had been lost since it erupted at 12:10 p.m. Sunday. The cause remained under investigation.

Overnight prospects looked good for firefighters, with temperatures dipping into the low 60s and humidity rising.

Meanwhile, California's biggest wildfire expanded to more than 104 square miles north of scenic Big Sur.

An army of more than 5,000 firefighters and a fleet of air tankers and helicopters made progress, however, surrounding 50 percent of the nearly 3-week-old fire.

Due to increased wind and flames from the spreading fire, Highway 1 was closed Monday night but reopened early Tuesday. More temporary closures could follow.

Some residents have been allowed to return to their homes, but some evacuation orders remained in place, while others were reduced to warnings.

Five state parks on Highway 1 between San Francisco and Los Angeles remained closed.

The fire, which has destroyed 57 homes, damaged three others and led to the death of a bulldozer operator in an accident, was caused by an illegal campfire.