A wildfire raging in northern Napa County exploded Saturday evening to 1,700 acres, according to Cal Fire, and continued to force the evacuation of residents from homes near the northwestern edge of Lake Berryessa.

The Snell fire is burning near Butts Canyon and Snell Valley roads, about 7 miles southeast of Middletown. It was 10 percent contained on Saturday night.

Fueled by hot and dry weather, the blaze was burning at a moderate rate of spread through grassy oak woodlands in a remote area difficult for crews to access, Cal Fire said.

No structures were reported destroyed but 180 are threatened. No injuries were reported.

Evacuation orders were in place for the west side of Berryessa Knoxville Road from Pope Creek Bridge to the Lake-Napa county line, Snell road and all roads to Snell Valley and Berryessa Estates.

Berryessa Knoxville Road is closed from Pope Creek Bridge to the county line, as is Snell Valley Road at the Butts Canyon Road intersection.

An evacuation center was established at the Pope Valley Farm Center, located at 5800 Pope Valley Road.

The cause of the fire is under investigation.

Residents living near the shore of Lake Berryessa have been confronted several times by explosive wildfire this year, starting with the 90,000-acre County fire earlier this summer. A second, smaller wildfire, the Steele fire, burned 135 acres but destroyed eight homes and damaged an additional four structures.

You can reach Staff Writer Robert Digitale at 707-521-5285 or robert.digitale@pressdemocrat.com. On Twitter @rdigit. You can reach Staff Writer J.D. Morris at 707-521-5337 or jd.morris@pressdemocrat.com. On Twitter @thejdmorris.