A temporary Do Not Swim notice has been put in place at Bertra beach near Westport.
People are being urged not to swim at the beach, following the detection of E.Coli in a water sample taken on Monday.
Mayo County Council says the bathing water at Bertra will be re-sampled, with results expected by Friday.
Mayo County Council says investigations are ongoing to identify the possible cause of the contamination.
While there are a number of other beaches around Clew Bay with excellent bathing water quality, Westport-based Councillor Christy Hyland says it's disappointing that Bertra beach is closed to swimmers at present.....