A Ventura County wildfire is threatening five 220-kilovolt power lines that supply Santa Barbara with electricity, authorities said Wednesday. More than 1,000 homes and a swath of oil-production fields are also in the fire’s path as it burns between Moorpark and Somis.

Fanned by high winds and aided by triple-digit temperatures and low humidity, the Guiberson Fire has grown to more than 16,000 acres since it ignited Tuesday near Fillmore. Despite the rapid escalation, fire officials said Wednesday afternoon that the blaze is 40 percent contained. Full containment is expected Saturday.

Air tankers are operating on the fire’s eastern and western flanks, and a dozen helicopters and more than 1,800 firefighters have been deployed to the scene.

Authorities say two outbuildings have been destroyed but no homes have been damaged. Moorpark College, about five miles south of the fire, has been closed. Two elementary schools, Campus Canyon and Walnut Canyon, were also closed Wednesday.

A preliminary investigation determined that the fire started Tuesday morning in a mulch pile off Guiberson Road near Fillmore.

Gov. Arnold Schwarzenegger declared a state of emergency for Ventura County on Tuesday night.

— Noozhawk publisher Bill Macfadyen can be reached at wmacfadyen@noozhawk.com. Follow Noozhawk on Twitter: @noozhawk.