The Kinney Fire in the Black Hills National Forest in southwestern South Dakota is about 40 percent contained.
Fire officials say they expect to fully contain the blaze Thursday. It is at nearly 2 ½ square miles but spread little on Wednesday as firefighters improved and reinforced containment lines on the fire's perimeter.
The cause of the blaze that began Tuesday northeast of Newcastle, Wyo., is still being investigated. No people have been evacuated and no structures harmed. About 185 people are battling the fire on the ground and from the air.