Nampa fire investigators are still working to determine what sparked the blaze, which broke out adjacent to Interstate 84 around 10 a.m. Thursday.
The blaze, which briefly closed a portion of the freeway, burned about 60 acres and took about two and a half hours to control, Nampa Fire Battalion Chief Todd Banta said. It burned west of the Northside Boulevard overpass.
Smoke from the blaze seriously impeded visibility in the area and caused several nearby businesses to evacuate, Banta said. The fire and smoke fouled traffic and prompted Nampa police to urge drivers to avoid the area.
Firefighters from Star, Middleton and Caldwell helped control the fire, Banta said.