Investigators believe 2,200 scorched acres near Dugway Proving Ground may have been the first "casualties" of the Firex '88 military exercise under way in the area.
No other major fires were being battled Saturday. Other blazes on the state's grasslands and hillsides had been brought under control.
Firex '88 is the largest military exercise to be conducted by U.S. artillery troops since the end of World War II. The exercise has brought thousands of National Guard and Reserve artillery troops to Utah's West Desert.
The blaze, which burned Bureau of Land Management land, may have been started by a spark from a vehicle's exhaust system, J.R. Davis of the Interagency Fire Center said Saturday night.
"There was a lot of military activity in the area, and we're thinking that Firex '88 may have had something to do with it," he said.
The fire was reported Thursday on Davis Mountain near Dugway and was brought under control Friday at 6 p.m.