There has been a fifth arrest in the investigation into the death of 18-year-old Niall Dorr in Dundalk, Co Louth, last month.
A man in his 20s was arrested today in relation to the incident on Castle Road on the night of 13 October.
Mr Dorr is believed to have been attacked by a group of up to seven people.
The man, who was arrested in the Dundalk area, is being detained at Dundalk Garda Station.
