An eyewitness said Bridgegate is currently closed along with the front entrance to Rotherham bus station.
Pictures on social media show a cordon set up near to the County pub.
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The air ambulance has attended as have the fire service, who are believed to be dealing with a person on the roof of a nearby building.
At this stage it is not clear if the two incidents are related.
Stagecoach announced earlier that the number 19 service was currently diverting via Mansfield Road and Eastwood Lane.
More to follow.