The Public Health Service has issued a warning against gathering any shellfish in the eastern Bay of Plenty for at least two weeks.
The warning applies to areas between Waihi Beach and the Whakatane River mouth.
Test show high levels of paralytic shellfish poison and people are urged to avoid any bi-valve shellfish taken from these areas.
Medical Officer of Health Dr Phil Shoemack says anyone who falls ill after eating shellfish should seek medical attention as soon as possible.
He says symptoms can include numbness and tingling around the mouth, dizziness, double vision, and in severe cases, paralysis and respiratory failure.
The warning's set to remain in place.