The public are being warned not to collect or eat any shellfish from a large stretch of the North Island's west coast found to have high levels of toxins.
The affected area extends from Mohakatino (located in Taranaki) north to Maunganui Bluff (just north of Dargaville), including the Manukau and Kaipara Harbours.
"Ongoing monitoring has shown high levels of Paralytic Shellfish Poison (PSP) present in shellfish along this coastline. People should take note of the areas that contain high levels of PSP and avoid collecting shellfish in these areas," Auckland medical officer of health, Dr Simon Baker, said.
Dr Clair Mills, Northland DHB medical officer of health, said anyone eating toxic shellfish is potentially at risk of illness.
"Cooking shellfish does not remove the toxin," she said.
People are being advised to avoid kina, mussels, pipis, tuatua, toheroa, oysters, cockles and scallops in the affected areas. Paua, crayfish and crabs can still be taken, however the gut should be removed before cooking.
Symptoms of PSP poisoning usually come about around 12 hours after eating affected shellfish.
These include numbness and tingling around the mouth and face, dizziness and difficulties with swallowing or breathing.
In severe cases, PSP can cause paralysis and respiratory failure.