Gardaí have this morning arrested a man in Co Louth in relation to the death of Paul Quinn in October 2007.
Mr Quinn (21), from Cullyhanna, Co Armagh, was lured across the Border and beaten to death in farm buildings near Castleblayney, Co Monaghan.
The man arrested today, aged in his mid-30s, is being held at Carrickmacross Garda Station under Section 30 of the Offences Against the State Act.
A total of 17 people have been arrested to date as part of the investigation carried out by the Garda and PSNI. Eight of those arrests have been made in the Republic, with nine others in the North.
The International Monitoring Commission (IMC) has said those behind the murder were either former Provisional IRA members or associates.
Sinn Féin has strenuously denied family accusations that members of the IRA were responsible.
Mr Quinn’s mother, Briege Quinn, has challenged the party's claims that the IRA was not involved.