Two separate investigations are under way into a pollution discharge into the River Allow near Kanturk, in north Cork at the weekend.
Both Inland Fisheries Ireland (IFI) and the Environmental Protection Agency (EPA) have confirmed that they were alerted to the discharge last Sunday on a stretch of the river popular with local anglers.
Both agencies say they have received no reports of dead fish to date.
In a statement, IFI said it is continuing to investigate the discharge which caused "significant habitat damage", with solids and sewage fungus visible on the bed of the river for several hundred metres.
IFI environmental officers have taken water samples and are awaiting analysis of the results.
No dead fish have been observed so far at the location but they will continue to monitor the scene, they said.
The agency, which has the statutory responsibility for the protection of Ireland's rivers and streams, also confirmed that the impacted site is not the same stretch of the River Allow affected by a major fish kill in June 2024 at Freemount.
The EPA confirmed it had been notified by North Cork Creameries in Kanturk, at 2.15pm on Sunday that a discharge to the River Allow had been stopped at 10am that morning.
In a statement, the agency said that it was aware that IFI had been onsite and had confirmed a discharge of polluting matter had occurred.
"At this time, we have not received any reports of a fish kill that might be associated with this incident," it said.
An investigation into the cause of the discharge is underway and they will issue a report in due course.
In a statement, North Cork Creameries said it identified a discharge of treated wastewater above normal levels.
It said that following an inspection of the nearby waterway, "it is our understanding that this has not been adversely affected, and we are carrying out tests to confirm this is the case".
It added that it had reported the incident to the EPA and while it continues to monitor the situation closely, there have been no further emissions of wastewater beyond normal levels.
"North Cork Creameries has comprehensive environmental protection systems in place and has invested very significantly in these systems over the past number of years.
"The co-operative is committed to environmental sustainability and protection throughout the entirety of its operations," the company added.
Meanwhile, last night's weekly angling training for some 30 young local anglers took place upstream of where the incident happened. Kanturk and District Trout Anglers Association would normally train at this spot.
