Twenty people have been poisoned since Friday in what the Bay of Plenty District Health Board is calling the worst outbreak of paralytic shellfish poisoning it has seen.
Ten of them were admitted for hospital care after suffering symptoms ranging from tingling around the mouth to difficulty walking.
Four remain in hospital including a 42-year-old woman in intensive care.
All had eaten shellfish collected from the Bay of Plenty shoreline.
Medical Officer of Health Neil de Wet says people should not collect shellfish from Tairua on the east coast of the Coromandel Peninsula through to Whakatane Heads in eastern Bay of Plenty.
He says the warning applies to all bivalve shellfish including mussels, pipi, tuatua, cockles, oysters and scallops as well as cat's eyes and kina.