The blaze, first reported at 5:50 p.m. at Young Wo Circle, sent smoke billowing over Folsom and the American River.
Flames reached the Folsom Corporation Yard by the Folsom Powerhouse. Two storage sheds burned. A Hazmat crew remains on the scene to determine if any toxic materials were affected.
Crews are protecting about 15 homes on Reading Street and River Way near the flames.
Folsom, Sacramento Metro and CAL FIRE firefighters are on the scene.
There is no word on what sparked the blaze.