Wexford County Council officials were last night investigating a serious marine pollution incident at the holiday village of Cahore Point, six miles south of Courtown Harbour.
As an unidentified black substance seeped into the harbour from a major drainage canal, council workers put up notices warning that bathing was unsafe.
The alarm was raised yesterday morning when locals noticed that large quantities of the oily-looking substance had covered areas of the sea and foreshore south of the small pier at Cahore Point, a popular swimming spot.
The Ballywater canal, known locally as the "main drain", empties into the sea from a covered channel which has an outlet halfway along the pier. It is at least 200 years old and drains some 30,000 acres of low, boggy land parallel to the coast.
Last night, the canal appeared to be full of the black substance for several miles and a strong smell hung over the area. County council biochemists took samples of the water yesterday, saying the results of their analysis should be known today.
Locals said they did not believe the pollution was agricultural as farmers in the area have spent thousands installing modern holding tanks for effluent.
A youth with a fishing rod yesterday claimed there had been signs of seepage of the black substance for several weeks.
The Ballywater canal extends for over three miles south of Cahore. A local farmer, Mr Paddy Synnot, said sluice gates near the canel outlet were no longer working and yesterday's high tide was pushing the polluting substance back up the canal.
There were fears that as the tide dropped, more of the pollutant would be released into the sea.
Large stretches of the Co Waterford coastline have been affected by an algae bloom which has caused Waterford Council Council to get scores of complaints from swimmers. The algae has affected the resorts of Tramore, Bunmahon and Annestown.
A council chemist, Mr Paul Carroll, said analysis had indicated that the algae bloom was nontoxic but had caused severe discoloration of the sea.