The Bagshaw Arms on Norton Avenue, Norton, was taped off overnight, with a police cordon in place between Mawfa Walk and Oakes Park View.
Officers are guarding the scene to prevent anyone from entering.
Details of the incident under investigation have not yet been released by South Yorkshire Police.
A man from the pub said that the incident was not related to the premises.
Another man, who loves close by, said when he arrived home at 4am this morning 'the area was swarming with officers'.