Because of the confirmed presence of blue-green algae, residents are urged to steer clear of using the waters of Marratooka Pond in Mattituck, and Georgica Pond in East Hampton, Suffolk County health officials said Friday.

That means no swimming or wading in the water, and keeping children and pets away from those areas, officials said.

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Any water looking “scummy or discolored should be avoided,” health officials said. If contact does occur, rinse off with clean water and see a doctor for symptoms that can include nausea, vomiting or diarrhea; skin, eye or throat irritation; and allergic reactions or breathing difficulties, the health department said.

Blue-green algae, also known as cyanobacteria, is naturally present in low numbers, but can increase, forming blooms of green, blue-green, yellow, brown or red, as well as floating scum, the county health department said in a release.