Seven people have sought hospital treatment after eating contaminated shellfish collected from the Mount Maunganui and Papamoa coastlines.
The patients complained of diarrhoea, vomiting, weakness and a tingling sensation around the mouth and face and on the arms and hands.
Two of those affected went to Tauranga Hospital's emergency department at the weekend, while five others presented themselves at Rotorua Hospital.
Tauranga-based Medical Officer of Health Phil Shoemack said the symptoms were caused by toxic shellfish poisoning and warned people not to eat shellfish gathered along the Bay of Plenty coastline or parts of Coromandel.
"The toxins can make people very ill and we strongly advise not consuming shellfish from any part of the affected area," Dr Shoemack said.
"The cases seen at local hospitals in the past day is a stark reminder of the risk of ignoring the warning."
One of the patients at Tauranga Hospital was treated and discharged on Saturday, as were three of those in Rotorua.
The three others remained in hospital in stable conditions yesterday afternoon.
Since August this year high levels of paralytic shellfish poison have been found in shellfish along a significant stretch of coastline.
A health warning is in place advising against the collection of shellfish from Tairua, on the east coast of the Coromandel Peninsula, south to Waihi Beach and along the Bay of Plenty coast to the Whakatane Heads in the Eastern Bay of Plenty.
The warning includes Tairua Harbour as well as Tauranga Harbour, Maketu and Waihi estuaries, Matakana and Motiti Islands, and all other inshore islands along this coastline.
The health warning applies to all bivalve shellfish, including mussels, pipi, tuatua, cockles, oysters, scallops, cat's-eyes and kina (sea urchins).
Paua, crayfish and crabs can still be eaten but, as always, the gut should be removed before cooking, Mr Shoemack said.
Consumption of shellfish affected by the toxin can cause numbness and tingling around the mouth, face or extremities; difficulty swallowing or breathing; dizziness; double vision, and in severe cases, paralysis and respiratory failure. The symptoms usually occur within 12 hours of a person eating the shellfish.
For information on health warnings in the Bay of Plenty visit www.ttophs.govt.nz and click on health warnings. Or call 0800 221 555.