Eleven Long Island beaches were closed to swimming Saturday due to concerns about bacteria levels.

Nassau County health officials ordered 10 North Shore beaches and one South Shore beach closed after officials cited the heavy rains that generate stormwater runoff, which can sweep bacteria and pathogens into local streams and bays, causing levels to spike.

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The North Shore beaches are Centre Island Sound, Creek Club, Lattingtown Beach, Laurel Hollow Beach, Piping Rock Beach Club, Pryibil Beach, Ransom Beach, Theodore Roosevelt Beach, Soundside Beach and Stehli Beach. Also, Biltmore Beach Club in Massapequa remained closed from earlier elevated bacterial levels, officials said.

Field 6 at West Beach and Field 8 at Overlook Beach, both at Heckscher State Park in East Islip, reopened to swimming Saturday after having been closed due to unacceptable water quality, the state Office of Parks, Recreation and Historic Preservation said. Field 6 at West Beach had been closed since Thursday.

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.