Pollution warning to swimmers
Swimmers have been told to stay out of the water at a popular beauty spot.
The Northern Ireland Environment Agency (NIEA) said there had been a "pollution incident" at the Cotton River which flows to Ballyholme beach in Co Down.
The source of the pollution has been traced to a farm.
In a statement, the Department of the Environment (DoE) said samples had been collected and legal action was being considered.
The DoE said: "The incident was investigated and the source has been traced to a farm property.
"Statutory samples have been collected with a view to possible prosecution through the Public Prosecution Service."
The local authority, Ards and North Down Council, has also been advised to erect posters warning of the pollution.
The DoE's marine division will carry out further water testing on Wednesday.