A fire that began Saturday afternoon has burned several hundred acres in neighboring Napa County.

The Knoxville fire was reported at 2:30 p.m. in the 15000 block of Berryessa-Knoxville Road north of Lake Berryessa in Pope Valley, according to Cal Fire.

Reports from the scene indicated it was burning in grass and oak woodland with a moderate rate of spread. No structures were said to be endangered.

By Saturday night the fire had grown to 400 acres, with 5 percent containment, Cal Fire said.

The number of personnel on scene quickly rose to 330, with Cal Fire, Napa County Fire and the California Department of Correction and Rehabilitation on scene, along with California Highway Patrol officers, Cal Fire reported.

The CHP reported that its officers and Napa County road crews were on scene to help with a road closure nearby.

Local fire districts – including South Lake County Fire, Lake County Fire and Northshore Fire – also sent firefighters according to reports from the scene.

Resources dedicated to the fire by late Saturday afternoon included 22 engines, 11 fire crews, five air tankers, five helicopters, five dozers and five water tenders.

Officials were reporting over the radio that they were having significant access problems to the rugged area, with wind recorded at 6 miles per hour, and gusts from the south southeast measured at up to 15 miles per hour.

Aircraft worked the fire aggressively throughout the afternoon. At one point the fire was reported to have shifted in the direction of Homestake Mine in Lower Lake.

The cost for the firefighting effort thus far has been estimated at $100,000, according to Cal Fire.

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