WHITEHALL, Mont. (AP) — Firefighting officials on Sunday called in additional resources to battle a wildfire burning Douglas fir, juniper and grass about 10 miles north of Whitehall in the Bull Mountains in southwestern Montana.

Officials say about 100 firefighters are battling the Antelope Fire that started about 2:30 p.m. Saturday and has grown to 462 acres in conditions officials describe as dry for this time of year.

Firefighters on Sunday worked to build fire lines along the south flank of the fire but not to the north in the direction it's heading because it's too dangerous. Two helicopters and four fire engines are also taking part.

Fire spokeswoman Leona Rodreick of the U.S. Forest Service says the cause of the fire remains under investigation.

She says no structures are threatened.