A brush fire broke out Monday morning in the Big Bear area and expanded to more than 300 acres hours later at the start of a warm week in Southern California. The Gold Fire in San Bernardino National Forest was estimated at about 350 acres late Monday afternoon with no containment.

A fire burning in the wilderness north of Big Bear Lake had charred 936 acres but wasn’t threatening any structures, the U.S. Forest Service said. It was generally headed to the northeast in steep terrain, with 500 personnel assigned to fight it.

Firefighters had built containment lines around 5% of the wildfire, which was burning in the Holcomb Valley area, about 5 miles north of Big Bear Lake