The U.S. Forest Service says a wildfire has broken out in the Bob Marshall Wilderness northwest of Augusta.

Lewis and Clark National Forest spokesman Dave Cunningham says the fire was reported Thursday afternoon and had grown to 200 acres within a couple of hours.

Even though it is burning in a wilderness area, Cunningham tells the Great Falls Tribune (http://bit.ly/OB8AN3) that firefighters are responding quickly because of the potential for rapid growth.

He says a crew of smokejumpers is at the scene supported by two air tankers.

Elsewhere, an uncontained fire burning in southwestern Montana on the Idaho line has grown to 2 square miles. No structures were threatened.