The potential sighting of a stoat on Aotea/Great Barrier Island has set off "alarm bells" at Auckland Council.
A predator detection dog has been called in to assist council and Department of Conservation (DoC) teams in finding the unwanted pest.
"With the speed stoats can cover the ground, it is vital to get on their trail as early as possible," said DoC operations manager George Taylor.
While pests like rats, rabbits, feral pigs, stray cats and skinks remain on Aotea/Great Barrier Island, stoats are public enemy number one.
"Getting a positive indication of stoat presence from the dog is the fastest way for us to know we have a problem and to start planning how to deal with it," said Mr Taylor.
Auckland Council says if stoats are back on the island, it could be "devastating" for local wildlife, including endangered birds like kereru and tuturiwhatu.
"Stoats, ferrets, weasels, plague skinks and even Argentine ants rely on people to transport them to our islands, so it's up to people to make sure they are not unwittingly introducing these devastating pests by thoroughly checking their gear and vessels before they leave the mainland," said incident controller Jonathan Miles.