Kershaw Beach in Canandaigua will remain closed through Monday, Aug. 10.
City officials extended the closure after harmful algal blooms were found in the water at Kershaw Park.
The beach can reopen if state health officials determine conditions are safe based on test results.
The city had already closed the public beach, dog beach and small craft launch Thursday afternoon and Friday because of blue-green algae.
The Canandaigua Lake Watershed Association reported 10 harmful algal blooms from July 31 to Aug. 6, with blooms found on both sides of the north end and mid-lake.
People and pets should avoid swimming, playing, jet-skiing or tubing through visible blooms.
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