Suffolk County health officials are telling swimmers to steer clear of Lake Ronkonkoma on the Brookhaven portion of the lake because of the presence of blue-green algae.

Exposure to cyanobacteria bloom, also known as blue-green algae, could cause stomach cramps, diarrhea, vomiting, headache, fever, muscle weakness and breathing difficulties, according to health officials.

Researchers from the Suffolk County Department of Health Services said Tuesday they have confirmed the presence of cyanobacteria at Lake Ronkonkoma and that it also persists in several other waters, including Sagaponack Pond in Southampton, Georgica Pond in East Hampton, Roth Pond at Stony Brook University, McKay Lake in Calverton, Fort Pond in Montauk, Kellis Pond in Bridgehampton, Wainscott Pond in Wainscott, Agawam Lake and Mill Pond in Southampton and Marratooka Lake in Mattituck.

The advisory covers only the Brookhaven portion of the lake; Lake Ronkonkoma Beach in the Town of Islip is open to swimmers, health officials said.

The algae create scummy or discolored water and contact should be avoided, health officials said.

If contact does occur, rinse off with clean water and see a doctor; if pets are exposed, call a veterinarian.

Blue-green algae are 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.

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CORRECTION: The extent of the health advisory was incorrect in a previous version of this story.