Firefighters were finishing mop-up duties Wednesday after the East Argyle Fire torched 107 acres earlier this week in the Southern Hills.
Les Madsen of South Dakota Wildland Fire said the fire started on Monday, when winds blowing as hard as 50 mph most likely re-ignited a smoldering slash pile.
The fire, which was northeast of Argyle, was contained Tuesday, and its cause remains under investigation.
Madsen said established trails in the area helped firefighters gain the upper hand and hold a line on the fire.
Firefighters from Argyle, Pringle and Custer volunteer fire departments, the Hell Canyon Ranger District and South Dakota Division of Wildland Fire battled the blaze.