Inland Fisheries Ireland has said it is investigating a fish kill in the Dunkellin River, in which up to 120 fish have died.
A suspected pollution incident occurred on a tributary of the Dunkellin River in east Galway last week.
Species of fish discovered dead include salmon, trout, perch, stone loach, stickleback, and lamprey.
Inland Fisheries Ireland (IFI ) staff were on site last Thursday and Friday to assess the event.
IFI said in a statement that it is actively probing the cause of this harmful event, and is now following a definite line of inquiry about a possible source of pollution.
Monitoring and assessment of the impact will continue to be undertaken to identify the cause of the fish kill.
IFI has notified other agencies about the incident including Galway County Council and the Environmental Protection Agency.
IFI works with other government agencies in line with the new national interagency protocol for investigating significant fish kills.
IFI is urging the public to report fish kills, water pollution, habitat destruction, or illegal fishing to its confidential 24/7 number, 0818 34 74 24.
