The owner of a beagle that became extremely ill after exercising at Minogue Park says the ordeal was "distressing" and she won't be walking her two dogs there until she finds out the cause.
Two other dogs who were exercised at the park have died.
Laura Dick walked her two beagles, Barry and Bella, at the off-lead dog exercise area at Minogue Park early on Saturday morning.
They walked the perimeter of the area for about 45 minutes.
"We got home about 7.15am and everything seemed alright," said Ms Dick. "I fed them breakfast and Barry started to look a bit funny, a bit wobbly. He quickly started shaking badly in his back legs."
Ms Dick phoned a vet and in the few minutes she was on the phone she could see Barry deteriorating further.
"We raced to after hours clinic. He started vomiting all through the car. By the time we got to the vet he couldn't walk, couldn't control bodily functions. He had things coming out of every orifice. It was really quite distressing."
It was coincidental that Ms Dick had arrived as the owners of two other dogs that had died were there and they established all three dogs had been exercised at Minogue Park.
Barry was medicated to control the tremors and given IV fluid and blood tests.
"We definitely know it was neurotoxicity," said Ms Dick. "It wasn't from rat bait anti coagulant."
She said Barry was found to have a small amount of rodent or rabbit bones in his system. However, she didn't notice Barry eating anything while they were at the park.
"He has devoured something while we at the park but I can only assume because if it was a rabbit carcass I would have had to drag him away. It must have been a very small piece and it could be coincidental."
Ms Dick took Barry home late Sunday evening, along with a $2500 vet bill for which she has insurance.
Ms Dick's other beagle, Bella, did not fall ill.
"Barry is very tired but he's in good spirits. Neurologically everything seems to be working okay, but it's too soon to find out if there are any lasting effects on his kidneys and liver."
Hamilton City Council's natural environments team leader Jeremy Froger said Council staff are working with other agencies to establish possible causes.
"One thing we are confident of is that it's not due to any poisons or pest control baits we use," Mr Froger said. "We haven't got any pest control operations under way in this park at present, and when we do, we make sure there are signs up warning park users.
"We're advising dog owners to stay close to their animals in the park until we have some more information on this risk, and how it can be addressed."
Mr Froger says NIWA has been asked to undertake tests of the water in Minogue Park's Lake Rotokaeo to establish if there are any potentially toxic algae, bio-matter of other chemicals or compounds present.
Nearby residents or park users who have seen any suspicious behaviour, people or substances in the park are urged to contact the Council's Parks and Open Spaces Unit immediately.
"We'd appreciate any help the public can offer here - we're very concerned about this and we want to find out exactly what is happening as soon as we can," Mr Froger said.
Minogue Park is a popular off-lead dog exercise area and the Council is keen to address the issue and allay community concerns about the welfare of dogs in the park.