"We strongly advise dog owners to either keep away from these areas for the time being, or keep their dogs on a leash."
The council was in contact with the owners of the dead dog and warnings had been put out.
"We have put signs up at Otamatea Reserve warning people that a dog who visited the park has died and to avoid the area or keep dogs on a leash," a council spokesperson said.
"Parks Team Leader Wendy Bainbridge has also been up to Otamatea and warned people walking their dogs."
About three months ago, the Whanganui Chronicle reported several dogs had fallen ill after being walked at Otamatea Reserve.
One of the dogs that fell ill was taken to Massey University for testing but the results were never made public.
The council says on that occasion it wasn't in contact with the owners of the dog and therefore could not ask permission for the results of the tests. It says it hopes to be able to share what happened to the dog that has died.
There were concerns the illness that struck dogs in July was related to rat poison and that it could have come from a nearby rest home.
But, that was denied by Philip Tebbutt, who owns the Virginia Lodge Rest Home next door to Otamatea Reserve. He said his organisation had never used rat bait.
Tebbutt said it was more likely that if rat bait had made its way to Otamatea Reserve it would have come from one of the households surrounding the park.
