The die-off of turtles in Flanders Bay has prompted state officials to temporarily ban the harvesting of shellfish and flesh-eating gastropods in portions of the East End.

Six Diamondback turtles collected late last month may have died after eating mollusks that harbored saxitoxin, a marine biotoxin that can paralyze and poison those who eat them, according to the state Department of Environmental Conservation and the Suffolk County Department of Health. Another dead one was found near West Meadow Beach in Stony Brook, state officials said.

The necropsies were not conclusive on the presence of saxitoxin, state officials said Monday, but circumstantial evidence and intestinal contents of the turtles show the way they died was consistent with paralytic shellfish poisoning.

Temporary bans on the harvesting of shellfish and gastropods, such as snails and conchs, are in effect for several thousand acres off Riverhead, Southold and Southampton towns. That includes the western portion of Flanders Bay in Riverhead, from Simmons Point to Goose Creek Point; all the tributaries leading to the bay; all the underwater lands in Terry Creek and Meetinghouse Creek; all the underwater lands in James Creek in Southold; and western Shinnecock Bay Southampton, state and county officials said.

Over the past several weeks, shellfish taken from these waters have tested positive for saxitoxin, authorities said.

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County health officials said they also tested water samples collected from Flanders Bay and its tributaries on Friday and results showed elevated concentrations of Alexandrium, the algae that produces saxitoxin. Health officials said the higher levels appear to be contained to Terry and Meetinghouse creeks but warned that the algae could spread to other areas.

Full results from the water tests are expected to be available later this week, authorities said.

Symptoms of paralytic shellfish poisoning depend on the amount of the toxin eaten, Suffolk health officials said. They can range from tingling of the lips and tongue to numbness in the face, loss of muscular control and difficulty breathing, authorities said in warning people to get medical attention as soon as possible.

People should avoid getting into discolored water but contact with water in and around areas closed to shellfishing is not expected to cause saxitoxin symptoms, health officials said. If contact does occur, rinse off with clean water immediately, they said.

More information about paralytic shellfish poisoning is at suffolkcountyny.gov/Departments/HealthServices/EnvironmentalQuality/Ecology/MarineWaterQualityMonitoring/HarmfulAlgalBlooms/RedTide.aspx and www.dec.ny.gov/outdoor/64824.html. For updated information on areas that are off limits to harvesting, go to www.dec.ny.gov/outdoor/7765.html.