The clinic advised people to avoid taking their dogs to the beaches until the issue had been resolved.
Abbotts Way Veterinary Clinic in nearby Remuera confirmed that about two weeks ago they had also treated a dog thought to have been poisoned by metaldehyde - the active ingredient in slug bait.
While unable to go into specific details, nurse Yani Riley said the dog was thought to have been on one of the beaches prior to presenting at the clinic ``tremoring and seizuring''.
Treating dogs for metaldehyde poisoning mostly just involved supportive care and trying to keep them as calm as possible.
"With the seizuring they also tend to overheat so it's important they're kept cool ... with towels and things,'' she said.
Auckland Council media advisor Lydia Blatch the council had been alerted to the reports. "There have been no new cases since Tuesday and all dogs are recovering.''
Vets treated dogs with similar symptoms in early September, Ms Blatch said.
The poisonings were not due to the council laying baits for pest birds, she said.
Auckland Council local parks manager Jane Aickin recommended pet owners keep an eye on their dogs or keep them on a leash while exercising on the affected beaches.
Council parks officers were carrying out regular checks of the beach, and warning signs were being installed.
Martin Hunter, who was at Kohimarama Beach with his daughter Kaitlyn, 13, and their dog Ruby said it was not unusual for there to be 20 dogs there at once.
There were times when dogs were not required to wear a lead so there was nothing preventing them sniffing around the public gardens and consuming whatever they found.
"There's always heaps of people walking their dogs around here, especially at this time of year so I would have thought having slug bait laid around here was a very silly idea.''
Cary Hogwood, a former professional dog trainer, was shocked to hear the news as she sat with a friend's dog on the St Heliers promenade.
"I've seen one dog come very close to being killed by slug bait poisoning before and I don't want to see it again,'' she said.
"They started seizing, shaking, drooling quite a bit and unable to stand up. That was only two small pieces of the blue slug bait.''
Fortunately a vet was nearby and they were able to get the dog to vomit.
"I think anyone who throws slug bait indiscriminately in a public place like this you have to really wonder about because, aside from anything else, kids can put them in their mouth and get very sick.''
