A prisoner in his 20s has been found dead at Castlerea Prison in County Roscommon.
The Irish Prison Service says next of kin has been notified.
Gardai are investigating 'all of the circumstances' surrounding the man's death.
The Irish Prison Service has confirmed to Midwest News today that the death in custody will be investigated by the Irish Prison Service, The Inspector of Prisons and An Garda Síochána, where circumstances warrant.
A post mortem examination is due to take place, and the results will determine the course of the investigation.
The man's name has not yet been released.