Johnny Nevin, 39, was arrested at his home in Templemore, Co Tipperary, on Saturday afternoon after gardaí were called to a disturbance in the area.
He is understood to have been drinking earlier in the day and became unwell while being held at the local station by officers.
Despite being taken to the Mid-Western Regional Hospital in Nenagh, he was pronounced dead on Saturday evening.
A post-mortem examination was to due to take place last night at the Mid-West Regional Hospital in Dooradoyle, Co Limerick.
The Ombudsman’s office has confirmed it was notified of Mr Nevin’s death under Section 102 of the Garda Act 2005, which states it must be contacted after deaths in custody. The watchdog has opened an investigation.
News of the incident comes after a man arrested on Tuesday evening was found dead in his cell at Tallaght Garda Station, Dublin.
The Ombudsman’s Office said Garda Commissioner Fachtna Murphy had referred the death to the independent investigators.
Last month the Ombudsman published a report on the death of Terence Wheelock, who died after being found unconscious in his cell at Store Street Garda Station, Dublin city.
It said gardaí did not cause the 20-year-old’s death in September 2005, though Mr Wheelock’s family have questioned the conclusions.