Two separate investigations have been launched into a protest at Cloverhill Prison in Dublin earlier.
One prisoner was seriously injured during the incident, which began this morning when a group of inmates refused to return to their cells after exercising.
The Irish Prison Service says about 15 prisoners in the B Yard refused to return to their cells, and that two men climbed onto an adjoining roof.
Prison management attempted to negotiate with the prisoners, but the situation is said to have worsened when one prisoner was assaulted by other inmates.
Control and restraint teams removed the prisoners following instructions from the Governor. A number of prisoners were injured and damage was caused to the building.
Separate investigations will now be carried out by the Prison Service and gardaí.
Five ambulances were seen leaving Cloverhill after the incident.
The Director General has commended management and staff for the 'professional manner' in which they dealt with the incident.
Separately, the Irish Prison Service has accused drivers with its escort service of engaging in "wildcat" industrial action.
The service says 33 prison escort staff reported for duty today, having "forgotten" their driver's licenses.
As a result they said they would not be able to fulfil their driving duties.
It is understood the drivers are in dispute over a new roster for the Prison Service Escort Corp (PSEC).
"The Irish Prison Service views this action as wildcat industrial action by individual staff which is in total contravention of all industrial relations practices and procedures," the Irish Prison Service says.
"Such action represents a serious breach of discipline and will be dealt with under the appropriate disciplinary procedure," it adds.
It says that escorts to the Criminal Courts Complex were delayed this morning as a result - but that all prisoners scheduled to attend court have arrived or are en-route.
The Irish Prison Service says it has been in ongoing consultation with the Prison Officers Association over a new roster for the PSEC.
