The Nassau County Department of Health said Friday swimmers should stay out of the water at five South Shore beaches because of concerns about elevated bacteria levels.

The advisory is a precautionary measure for beaches known to have substantial storm water runoff caused by heavy rainfall. The runoff can raise bacteria levels, which results in the waters failing to meet state standards for swimming, health officials said.

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The beaches covered in the advisory include Biltmore Beach Club, Massapequa; Hewlett Point Beach, East Rockaway; Island Park Beach, Island Park; Merrick Estates Civic Association, Merrick; and Philip Healey Beach, Massapequa.

The department said the advisory will be lifted 8 a.m. Saturday unless there is additional heavy rainfall or water samples reveal elevated bacterial levels.

For recorded information on beach closings and openings in Nassau, call 516-227-9700. Health department representatives are available weekdays from 9 a.m. to 4:45 p.m., at 516-227-9717.