An international angling competition on the River Shannon has been cancelled today after a major oil spillage on the river near Athlone.
The Midland and District Coarse and Pike Anglers Club have said that authorities must redouble their efforts to deal with the pollution.
They said only a vain attempt is being made to save one of the best known fishing stretches in the country from a complete environmental and ecological disaster.
Westmeath County Council said it has now treated all contaminated areas identified on the Shannon and Al Rivers.
However, it said the source of the pollution remains unknown and locals say the oil slick has now moved to the old canal in the town of Athlone.
A number of swans and other wildlife have been removed to the Kildare Animal Foundation where they are been treated successfully for oil damage.
Separately, in a statement released a week after the spill, the National Parks and Wildlife Service said it was "made aware of an oil spill near Athlone " and that its local staff "were on the ground assessing the potential damage to local wildlife over the course of the weekend and every day since".
The organisation added that it is working closely with Westmeath County Council, Inland Fisheries Ireland and Waterways Ireland to identify areas most at risk.