Members of the public are being asked not to swim at Balbriggan beach.
Fingal County Council's put a temporary 'Do Not Swim' notice in place.
It's due to an overflow at Quay Street Pumping Station in Balbriggan, which happened as a result of yesterday's heavy rain.
Fingal County Council spokesperson Gerry McDermott hopes tests on bathing water samples will lead to the ban being lifted.
He says the notice is cautionary pending laboratory tests on samples which are scheduled for early next week. If the samples are clear, the beach will be re-opened.