Blue Green algae has been confirmed at the lake in Lurgan Park.
Members of the public are urged to avoid the water and keep pets away from the lake.
Angling will also cease until further notice.
As a precautionary measure, warning signage has been erected at the site to warn visitors of its presence and advise that adults, children, and animals should avoid contact with the algae and the water close to it due to its harmful effects.
Swallowing the water can cause stomach upsets or severe illness to people and death to animals. Contact with the water or the blue-green algae can also cause rashes and skin problems.
Members of the public are advised to report concerns using the Bloomin’ Algae App to help provide a rapid and more comprehensive picture of harmful algal blooms in the area and inform the relevant environment agency, local authority or landowner.
You can report blue green algae here.