Commercial oyster farms in north Auckland have been closed as a problem with a potentially fatal toxic shellfish disease spreads.
The Ministry for Primary Industries has extended a warning it issued for parts of Whangaparoa last week for people to not collect or eat shellfish.
Tests show higher-than-safe levels of Paralytic Shellfish Poisoning toxins, which can cause death in severe cases.
The extended warning area stretches from Takatu Point, north of Kawau Island, to Toroa, or Gull Point, in the south of the peninsula.
It includes the Mahurangi Harbour, Kawau Island and other small islands nearby.
The ministry said the oyster farms were closed as a precaution and were being monitored.
People should not eat mussels, oysters, tuatua, pipi, toheroa, cockles, scallops, cat's eyes, kina and all other bivalve shellfish.
Paua, crab and crayfish can be eaten only if the gut is removed before cooking.