Health officials have labelled an outbreak of paralytic shellfish poisoning as the worst seen in the Bay of Plenty.
Since last Wednesday, 20 people have been poisoned by eating shellfish collected from the Bay of Plenty shoreline.
Ten were admitted for hospital care after suffering symptoms ranging from tingling around the mouth to difficulty walking. Four people remain in hospital.
The levels of toxins being reported from routine shellfish sampling, and the number and severity of cases underline that collecting shellfish from the affected area is a significant health risk.
The health warning that was issued in August remains in place.