Two men and one woman have been arrested in Drogheda, Co Louth, as part of an investigation into the murder of Seamus McMahon on 21 March 2010.
The men are both in their 20s and the woman is in her late teens.
Mr McMahon, 41, from Green Acres in Dundalk, was visiting a woman in the Saltown area of Dundalk when he was shot dead in March 2010.
The three are being detained under Section 30 of the Offences Against the State Act at Drogheda and Dundalk Garda Stations.
A total of seven people have now been arrested as part of the investigation.
