People are being warned not to collect shellfish from a bay in the Marlborough Sounds because of a potentially dangerous toxin.
Ministry for Primary Industries has issued a public health warning about collecting shellfish from Onapua Bay, after tests found high levels of Paralytic Shellfish poisoning there.
The ministry said tests on shellfish in the area showed levels of the toxin were more than triple the safe limit.
"Routine tests on shellfish samples taken from Onapua Bay has shown levels of Paralytic Shellfish poisoning at 2.6 mg/kg," the ministry said.
The safe limit was 0.8 mg/kg.
Anyone who ate shellfish, including mussels, oysters, scallops, tuatua, pipi, toheroa and cockles from the bay were at risk of getting sick.
Cooking shellfish would not remove the toxin, the ministry said.
It also advised people to take care when eating paua, crab and crayfish, ensuring they remove the gut of the fish before cooking.
"Toxins accumulate in the gut. If the gut is not removed its contents could contaminate the meat during the cooking process."
"Symptoms typically appear between 10 minutes and 3 hours after ingestion and may include numbness and a tingling around the mouth, face, and hands and feet, difficulty swallowing or breathing, dizziness, headaches, nausea, vomiting [and] diarrhoea."
In some cases, the toxin can be fatal.
The ministry would continue to monitor shellfish at the site.