Five young men have been injured at the Oxegen Festival at Punchestown Racecourse in Co Kildare.
The victims are believed to have received slash wounds following an incident shortly after 4am in the Blue Campsite.
Four of the men, who are all in their late teens, had their injuries treated on site, but a fifth man, aged 19, has been taken to Tallaght General Hospital.
Gardaí have notified the families of the injured men.
Four of the five are from Northern Ireland.
Gardaí have recovered a weapon and have appealed for any witnesses to the incident to contact Naas Garda Station on 045-897333, the Garda Confidential Line 1800-666111 or any garda station.
