Firefighters expect to have the Range 12 Fire that was moving toward the Hanford nuclear reservation contained by Thursday.
Wednesday it was 60 percent contained, up from 20 percent Tuesday.
Crews were starting to be released from the fire Wednesday after they kept the fire perimeter intact during a red flag weather warning issued Tuesday because of winds and low humidity.
There were about 228 firefighters and staff assigned to the 275-square-mile fire Wednesday, down from 404 earlier. One helicopter, one bulldozer and 27 fire engines also were at the fire.
Wednesday firefighters were continuing to reinforce containment lines along the 117 mile perimeter of the fire.
A temporary flight restriction over the fire area has been lifted. The restriction was ordered after a drone interfered with firefighting efforts over the weekend.
The cause of the fire, which started Saturday on the Yakima Training Center, has not been determined. No one was injured in the fire.