37 illegally held mobile phones have been found during a major search in the maximum security prison in Portlaoise.
The search was carried out in the prison's E wing, which houses subversive prisoners.
Dissident Republican prisoners were removed from their cells and the landing areas when the search began at 7am.
It was led by the Operational Support Group, a unit of specially-trained prison officers.
A Prison Service spokesperson said the search has been completed and the discoveries are now a matter for Prison Service authorities and the gardaí.