A warder has been knocked unconscious when prisoners clashed with staff at a jail in Northern Ireland.
Two others were injured when they were attacked at Maghaberry, near Lisburn, Co Antrim.
The trouble flared on Wednesday night after three prisoners refused to return to their cells after they had been using pay phones.
The officer who was knocked out hit his head on a pillar. One officer received cuts behind his ear.
A spokesman for the Northern Ireland Prison Service said that the jail's governor Pat Maguire had launched an internal investigation into the incident.
Meanwhile the search for a new director general of the prison service has started. Applications for the job to replace Colin McConnell - which carries a salary of up to £160,000 - close on May 4.
Mr McConnell is moving at the end of next month to head the Scottish Prison Service. The current deputy director director Max Murray will act up until the position is filled.