An inmate has been found dead in his cell in Mountjoy.
Douglas Ward was serving ten years for killing an 18-year-old in Dundalk in 2010.
Medical guards rushed to his aid, but he was pronounced dead a short time later.
Officials are liasing with the family of the man who was serving time for manslaughter.
The matter's being investigated by the Governor of Mountjoy and as with all deaths in prison, a separate inquiry's being launched by the Inspector of Prisons.
The Irish Prison Service says a post mortem will be carried out later.
