A major fish kill is being investigated on an environmentally sensitive river in Co Cork in which at least 5,000 fish have died.
The investigation is being conducted by Inland Fisheries Ireland (IFI), the State agency responsible for the protection and conservation of freshwater fish and habitats.
The affected river is the River Allow, a tributary of the Munster Blackwater catchment and the pollution incident occurred near Freemount in the north of the county in an area designated as a Special Area of Conservation.
Uisce Éireann has a water treatment plant in Freemount and said it is investigating a reported spillage at the plant.
IFI officers are attempting to determine the scale of the fish kill and have observed dead fish in the river 4km downstream of the suspected source location.
Species of fish discovered dead include juvenile Atlantic salmon, brown trout, lamprey, eel, stone loach, roach, and dace.
The river also supports a population of freshwater pearl mussel, as well as being an abundant salmon and trout habitat.
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Water samples have been taken from the river to gather evidence of the discharge, the source point of contamination, and advance any potential prosecution according to IFI.
In a statement, Uisce Éireann said that it is carrying out an investigation and clean-up operation following the incident.
It said that it is cooperating with the IFI and has notified the Environmental Protection Agency and National Parks and Wildlife Service.
The company said that measures have been taken to "ensure there can be no further discharge from the plant".
Uisce Éireann also said that there has been no impact on the quality of drinking water.
'A scene of devastation'
Inland Fisheries Ireland Director for the South West Region has described the fish kill as an ecological disaster at a time of already significant biodiversity loss.
Speaking on RTÉ's Morning Ireland, Sean Long said that a local environmental officer was met by "a scene of devastation" when he went to examine the River Allow on Sunday, following reports of a spillage at a nearby Uisce Éireann facility.
"The river was littered with dead fish," he said, "and there were no insects or any indication of life in the area".
Mr Long said up to eight kilometres of the river has been affected and the incident has set back the area of special conservation by years.
He told the programme that they have a "fair idea" of what caused the damage.
"We have spoken with staff at the local treatment plant and had full assistance and co-operation from the local authority," Mr Long added.
The fish kill has led to the cancellation of the Trout Anglers Federation of Ireland's All-Ireland River Championship, due to take place in the coming days, according to Michael Twohig of the Kanturk Trout Anglers Club.
"Unfortunately, because of the amount of dead fish flowing from the Allow into the Dalua River, the competition has to be cancelled completely.
"This is obviously devastating for the local economy."
Mr Twohig, who is also chairman of Integrated Rural Development Duhallow, which was set up to improve river quality in the local area, said all angling on the river for "our own local club competitions", has also been suspended.
"We will have to make a decision in the next few weeks as to whether we will allow recreational angling because we will need need more detail about what substance has been leaked into the river."
Mr Twohig said he did not know if there was a public health issue, adding more information was needed.
