Bay of Plenty residents are being warned to avoid collecting or eating shellfish.
Testing has confirmed high levels of paralytic shellfish poison along the Coromandel and Bay of Plenty coastline.
The area stretches from Tairua Harbour to Bowentown heads.
Medical Officer of Health Dr Jim Miller, says it affects mussels, pipi, tuatua, cockles, oysters, scallops, cat's eyes and kina.
He says paua, crayfish and crabs can still be taken, but the gut should be removed before cooking.
Dr Miller say it's unfortunate the warning has had to be reinstated, but it's a natural occurrence which is difficult to predict.