A harmful blue-green algal bloom has been found in a third pond in Southampton, the Suffolk County Department of Health said Thursday.

The discovery of cyanobacteria in Wickapogue Pond means four water bodies in Suffolk County are now afflicted with the bloom, according to the New York State Department of Environmental Conservation.

Mill Pond and Lake Agawam in Southampton and Big Reed Pond in Montauk also have confirmed outbreaks of cyanobacteria, according to the DEC's website.

The bacteria, which turn the water a murky green, release toxins that can be dangerous to people and animals, according to the department.

The blooms, which occur when cyanobacteria overgrows in a water body, can cause gastrointestinal upset and allergic reactions, among other symptoms, in people and animals, according to the county health department.

The county advised people to stay away from the affected waters and to keep their pets and children away from the areas.

A Jack Russell terrier died in 2012 after drinking water from Georgica Pond in East Hampton during a bloom.

Last month, a bloom was found in Marratooka Lake in Mattituck, but that water body has since been removed from the DEC's list of active algal blooms.

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