Update: The Irish Prison Service has said it is investigating the death of a prisoner at Cloverhill in Dublin.
In a statement, it says all practicable measures are taken by prison management and staff to ensure the safety of those in custody.
However, it says regrettably no prison system can be completely free of violence and inter prisoner assaults do occur.
The man in his 30s died last night after an incident involving two inmates at around midnight.
It adds that gardaí and the office of the Inspector of Prisons are also investigating the circumstances surrounding the incident.
Gardai say they are following a definite line of inquiry after the body of an inmate was found in Cloverhill in Dublin.
A post mortem is being carried out this evening.
Shortly after midnight gardaí and emergency services were called by prison authorities following an incident involving two male prisoners in custody at the prison.
A man in his late 30s was treated by emergency services but was pronounced dead at the scene a short time later.
The man's body remains at the scene which is currently preserved pending a full forensic and technical examination.
Gardaí say they are following a definite line of inquiry and the investigation is ongoing.