BBCInvestigations are being carried out at Portstewart StrandPeople have been advised to not enter the water at Portstewart Strand in County Londonderry as officials investigate a "potential water pollution incident".
The Department of Agriculture, Environment and Rural Affairs (Daera) said it was made aware of the incident at the popular beach at 20.18 BST on Tuesday and has issued a temporary advice against bathing notice.
The Northern Ireland Environment Agency's (NIEA) pollution response team and Daera marine staff are now investigating the source of the suspected pollution.
As a precautionary measure on Wednesday, Daera said swimming was not recommended and that dogs must be kept on leads and away from the water.
Cause yet to be confirmed
A spokesperson for Daera said the advice was "intended to protect public health while further information is gathered".
The National Trust, which manages the beach, said officials from Daera and Northern Ireland Water were at the site on Wednesday carrying out investigations.
A spokesperson said the pollution could potentially be linked to food waste or grease entering the sea via the River Bann, but that the cause had not yet been confirmed.
"We are waiting for Daera Bathing Water to carry out sample testing and we will keep the advice against bathing in place until we know that the water is clear," the spokesperson said.
The temporary notice will remain in place while water samples are analysed and investigations continue.
Northern IrelandNatureCauseway Coast and Glens Borough CouncilPortstewartEnvironment
