VERNAL, Utah (AP) -- A Diamond Mountain blaze on mostly Bureau of Land Management land has grown to 2,600 acres.
Officials Thursday estimated the fire was 20 percent contained.
Investigators are still trying to determine the cause of the fire, which was sparked Tuesday.
Two heavy air tankers, three helicopters and two Hot Shot crews battled the fire Thursday.
Officials reported steep, rocky terrain and little access to most of the land.
The fire had spread to some tracts of state and private land, but no structures were immediately threatened.