The so-called Robbers Fire is threatening the town of Foresthill, prompting the evacuation of some 300 homes.
Fueled by hot and dry conditions, the fire is just 10 percent contained and has burned 800 acres. It's currently threatening 150 homes.
Firefighters fear the flames could jump the American River and also threaten the town of Colfax.
Gov. Jerry Brown has called in more firefighters and the California National Guard to battle the blaze.
The Associated Press contributed to this report.