A fire at the intersection of U.S. Highway 91 and Tyhee Road started from an excavator trying to load rocks into a truck, Monday afternoon.
Employees at E&G Contractors tried to put it out, but the flames spread like gasoline into the grass, said E&G employee Ellen Jensen.
The shop at E&G burned, but the office was saved.
The rocks were intended for victims of the Charlotte Fire, which ravaged a neighborhood in nearby Pocatello more than a month earlier.
The fire was threatening other barns and outbuildings, though no homes appeared to be threatened.
Idaho Power had shut down power lines in the area.
The fire had closed the intersection to traffic.