Firefighters from several agencies knocked down a 75-acre brush fire that closed a portion of Highway 155 Wednesday, officials reported.

The Kern County Fire Department said firefighters would remain on the scene, in the area of Keyesville just west of Lake Isabella, overnight and into Thursday to complete mop up of the fire.

All roads through the area were reported open at 9 p.m. Thursday. No structures were threatened.

The first report of the blaze was called in by a medevac helicopter just before 3 p.m. Due to the remote location and steep terrain, firefighters had to hike in with hose lines until air resources arrived on scene, Kern County Fire officials said.

Five air tankers and three helicopters were among the responding units. Crews were able to place hose lines around the fire.

The fire closed a portion of Hwy. 155 after a spot fire jumped the road but firefighters were able to quickly douse it and the road was reopened a short time later.

Agencies responding included Kern County Fire, the US Forest Service and the Bureau of Land Management. The cause wasn't immediately known.