A woman has been arrested in connection with the murder of Seamus McMahon in Dundalk on 21 March 2010.
The woman, who is in her 20s, was arrested this morning in north Louth.
She is the fourth person arrested as part of the investigation.
Mr McMahon, 41, from Green Acres in Dundalk, was visiting a woman in the Saltown area of Dundalk when he was shot dead.
