The prison service has revealed that inmates at the Midlands Prison in Portlaoise mounted a protest yesterday after attempts to get drugs into the jail failed.
A package of heroin was apparently thrown over the wall of the prison, but it was recovered by guards before the prisoners could find it.
The seizure sparked a protest in the prison yard and some inmates reportedly smashed hand basins and toilet bowls in their cells.
Prison officers entered the cells in riot gear and restored calm a short time later.