One man was killed and another injured in an incident late on Christmas Eve.
Gardai said the man's death at a premises in Courtown Harbour in Co Wexford is being treated as suspicious.
The alarm was raised at about midnight.
The injured man was taken to hospital for treatment and Garda technical officers are to carry out forensic examinations at the scene.
Later, gardai said the dead man was aged in his 40s.
He was found with a fatal stab wound at a house at Ballinatray Lower in the town.
The injured man, who was arrested after being released from Wexford General Hospital, was also aged in his 40s.
He was being questioned under section four of the Criminal Justice Act at Enniscorthy Garda station.
A post mortem on the dead man is to take place in Waterford tomorrow.