Around two dozen riot police are currently at Rotherham Town Hall, which has been barricaded by an armed man since this morning.
Negotiators are still in talks with the man, according to reports.
South Yorkshire Police were called to the scene at around 9.45am this morning due to reports of an alarm going off.
Emergency services attended and a man was found to be in the building.
The man, who is believed to be armed with a hammer, remains in the building.
Nobody else is thought to be in the Town Hall at this time.
A cordon is in place at the scene and The Crofts is still closed to traffic.