An area of open land off Station Road, close to Moss Way, Mosborough, has been taped off.
Passers-by said officers are guarding the cordon and sniffer dogs have been deployed.
Officers have been seen searching the grassland.
POLICE: Thieves steal 14 cars from SheffieldÂ garage in overnight raid There are a number of police vehicles at the scene.
Details on the nature of the incident under investigation have not yet been released by South Yorkshire Police.
More to follow.