Operations at a power plant in the midlands have been suspended after a hot water discharge into the River Shannon.
It happened at the Lough Ree Power Station in Laneborough in Co Longford.
Concerns have been raised surrounding the potential affects on fish and other wildlife in the river.
In a statement, ESB said it was shutting down the plant for the coming weeks.
It also added that is trying to change its environmental licence regarding the temperature of the cooling water it pumps into the Shannon.
The EPA has said that is investigating the incident which occurred yesterday at Lough Ree Power Station.
Sinead O'Brien from Sustainable Water Network said: "That to me sounds as if they are trying to get the licensing conditions made a little bit more less onerous to facilitate them to continue rather than actually looking seriously at the impact and coming up with measures to address them.
"And there are measures that can be used like cooling ponds to be used within the facility itself to bring down the level of the temperature before it goes into the water."