A 50 year old man has been arrested as part of the investigation into the murder of Paul Quinn in Co Monaghan last year.
The man was detained shortly before 9.30am in Dundalk and is being held in Monaghan garda station under Section 30 of the Offences Against the State Act.
Mr Quinn (21), from Cullyhanna, south Armagh, was beaten to death by a masked gang on October 20th, after he was lured to empty farm buildings in Castleblayney, Co Monaghan.
A number of arrests both sides of the Border have been made in recent weeks
In May, the Independent Monitoring Commission found that the IRA did not kill Mr Quinn, but said "local members or former members" had been involved in the incident.