An investigation is underway into the illegal dumping of six calves in the Riverstown River, a tributary waterway in the Downs, near Mullingar, Co Westmeath.
Westmeath County Council has said it is investigating the serious incident along with the Department of Agriculture, Food and the Marine and An Garda Síochána.
All three agencies are carrying out independent investigations into the matter, it said.
A spokesperson for Westmeath County Council said: "The failure to dispose of deceased livestock in a responsible and lawful manner is not only an environmental offence, but it also undermines good farming practices and poses a risk to the wider community."
The local authority is reminding farmers of their legal obligations to ensure that deceased animals are managed appropriately.
All dead livestock must be collected promptly by registered animal disposal operators, in accordance with national regulations, the council said.
Westmeath County Council is urging members of the public to remain vigilant and to report any incidents of illegal dumping or environmental damage.
