A wildfire burning 100 miles north of San Francisco has spread into Napa County as it expanded to 26 square miles.

The California Department of Forestry and Fire Protection said early Wednesday that crews had the flames 6 percent contained, a slight uptick from Tuesday evening's figure. Full containment isn't expected until Monday.

At least 150 people have been evacuated and many more were advised to leave their homes as the fire chews through dry timber and brush in Lake and Napa counties. No vineyards are threatened by the flames.

The fire erupted Sunday several miles from the community of Lower Lake.

More than 1,100 firefighters are battling the blaze that is threatening 50 structures. No homes have been destroyed, and no injuries have been reported.