Health officials say about nine miles of beaches, from Barnegat Light to Ship Bottom, were closed around 12:30 p.m. Saturday after several "home-generated" insulin syringes and other waste was found during beach-cleaning operations at high tide.
Also found floating in the water were large amounts of eel grass, wood and some plastics.
Officials say recent storms, high tides and wind conditions likely spread the debris.
They also believe some of it may have come ashore from combined sewer overflow systems or from the inner shorelines of the New York/New Jersey harbor areas.
No injuries were reported.
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