After being closed as a precaution, all Nassau County beaches operating for the season have been reopened, the county Department of Health said Wednesday.

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Heavy rains closed 19 beaches Monday and Tuesday because of concerns over bacteria. After such rainfall, stormwater runoff can sweep bacteria and pathogens into local streams and bays, causing bacterial levels to spike, according to health officials.

Health department representatives can answer questions about beach closings weekdays from 9 a.m. to 4:45 p.m., at 516-227-9717.