The annual report on penal statistics in prisons by the Council of Europe identified Ireland as one of 15 countries in Europe where prisons have more inmates than places available.

All four males have since been released without charge. A file will be prepared for the Director of Public Prosecutions.

Officers investigating the smuggling of controlled drugs and contraband into prisons have carried out searches.

Mr O’Callaghan said it was his belief that laws allowing judges to refuse bail where they believe there is a risk that the person would go on to commit another serious offence are being applied.

The call for greater measures to prevent and detect contraband in prisons follows the death of a prisoner a few hours after reports he had consumed drugs and home-made alcohol in Cloverhill Prison in Dublin three years ago

The hearing will take place behind closed doors.