Containment on the Highway Fire jumped to 90 percent Thursday morning, according to fire officials.
The size remains steady at just over 1,500 acres. Full containment is expected by Sunday, according to the interagency InciWeb information site.
The fire burning southwest of Lake Isabella was discovered last weekend and temporarily closed a portion of Highway 178. All but one westbound lane have since reopened, and officials say they expect that lane to open Thursday night.
Hundreds of firefighters have battled the blaze from the ground and air. They're now in the "line construction and mop up" phase and will demobilize resources as appropriate, according to InciWeb.
There are no dangers to the populated areas of the Kern River Valley.
The cause of the fire is unknown.