Brookings firefighters extinguished a half-acre grass fire in southern Brookings County on Tuesday afternoon.

Volunteers were called to the scene, about a quarter-mile north of the Brookings-Moody county line along County Road 77, at 4:40 p.m.

They worked to put out the flames near the Big Sioux River for about 50 minutes.

Deputy Fire Chief Pete Bolzer said the cause of the fire is unknown at this time and remains under investigation. No structures were threatened by the blaze, and no injuries were reported.