Gardaí say no foul play is suspected following the deaths of two prisoners in the last 24 hours.
At the Midlands Prison, officers found an inmate in an unresponsive state at 6:30 this morning.
Efforts to revive him failed and the man, who was in his thirties, was pronounced dead in hospital an hour later.
Yesterday morning, an inmate at Mountjoy was found dead in his cell.
He was 39-year-old Douglas Ward, from Knockbridge, County Louth.
He had been serving a sentence for the manslaughter of 18-year-old Niall Dorr from Dundalk in 2010.
