Up to 35 Mountjoy prisoners are to be charged "imminently" for their role in a riot at the prison in July when over 70 inmates barricaded themselves into a recreation room and caused damage estimated at around €80,000.

Three prison officers and five inmates were injured in the riot on 12 July. After barricading themselves into a recreation room, the prisoners managed to break into adjacent workshops. The computer room, woodwork room, general education room and the recreation room were damaged in the disturbance.

Inmates seized hammers and planks of wood after breaking into the woodwork room and were disarmed only when over 70 prison guards in riot gear, backed by another 30 guards, moved in after a stand-off that lasted several hours.

Prison sources have estimated the damage at €80,000. Prisoners themselves were involved in repairing much of it. In-house IT experts were also able to fix some of the broken computers. Professionals were hired to mend the damaged floors and floor coverings, locks and doors.

No high-profile prisoners are to be charged in relation to the incident but many mid-level drug dealers are to be charged.

The culprits will be brought before Dublin district court in the coming weeks to be charged with offences ranging from assault, threatening behaviour and causing a disturbance.

The initial charges are in relation to criminal damage as a result of the riot but more are expected to follow in relation to assault of prison officers. The most seriously injured officer sustained serious facial and dental injuries when he was hit in the face with a fire extinguisher. He has since returned to work.

The two other injured officers inhaled foam from the fire extinguisher when prisoners sprayed them with it as they broke through the barricade.

Prison CCTV footage assisted gardaí in identifying some of the people involved. Prison officers were also able to help gardaí with their enquiries and identification of some of those involved. After the riot, a dozen of the ringleaders were transferred to other jails.

The disturbance began in the late afternoon in a basement recreation room in the D Wing of Mountjoy. Only two prison officers were on duty in the recreation room when a large number of inmates began throwing pool balls and pool cues at them and turning over tables.

The prison service said the riot related to prisoners' mounting anger at tough new security measures put in place to prevent the smuggling of drugs and other contraband into the jail. But overcrowding has also been an issue at the prison. Well over the 420 inmates – the prison's capacity – were housed at Mountjoy at the time of the riot.

In the days after the riot, the Prison Officers Association (POA) cited overcrowding as a "contributory factor", saying it was "deeply concerned" and had repeatedly warned management about the potential for violence in Mountjoy and other prisons.

Figures obtained by the Sunday Tribune show that, four days after the riot in Mountjoy, eight of the jails were operating at above their full capacity. Several others were operating at well above their original capacities, as cells have been doubled up using bunk beds and mattresses.

The Irish Prison Service said in a statement at the time: "It has to be acknowledged that the Irish Prison Service must accept all prisoners committed by the courts and we do not have the option of putting up 'house full' or 'no vacancies' signs. It is quite clear that we are operating at near, or slightly in excess of, our bed capacity at this time. We are subject to peaks and troughs and July is traditionally the busiest month of the year for committals."