The Auckland City Council is warning dog walkers to watch out for toxic sea slugs after three were discovered on Kohimarama beach.
The council has put warning signs on the beach following the discovery on Monday and says it will be monitoring the area for further sightings.
Last year, several dogs became sick and five died after visiting beaches around the Hauraki Gulf.
Scientists blamed tetrodotoxin, a poison found in sea slugs, for the deaths.
The council says the cause of the dogs' deaths was never established, but the poison is very toxic to dogs and potentially toxic to humans.