Two investigations are under way after a prisoner was held hostage in Mountjoy jail this evening.
The inmate was later taken to hospital for treatment of his injuries.
It is understood the prisoners holding him were armed with makeshift knives and that he suffered cuts to his head.
His injuries are not believed to be serious.
The incident began at around 6.30pm when all the inmates in the prison were on recreation
They were immediately returned to their cells and the prison was locked down.
Senior officials from the Irish Prison Service, some of whom are trained in negotiations, along with the director of operations were in Mountjoy when the situation was resolved just before 9pm.
The five inmates involved have now been segregated.
