Idaho 16 was reopen Monday evening between Chaparral Road and Jackas Gulch Road south of Emmett as crews mopped up after a brush fire.
Firefighters from Eagle, Fire, North Ada County, Meridian, Boise, Gem County and Bureau of Land Management responded.
The Ada County Sheriff's Office said commanders on scene estimated that the fire burned between 30 and 40 acres. No structures were involved.
Investigators were trying to determine how the fire started.