However, Auckland Council's research investigations and monitoring unit (RIMU) is convinced sea slugs are not to blame.
"We have been getting reports of dogs becoming sick over the last couple of weeks, and each dog has recovered. Previously when we saw dogs that had consumed sea slugs and eggs they would die because the toxins are so strong,'' said Dr Jarrod Walker, a senior marine scientist with the unit.
"On Saturday I did a two hour walk on Kohimarama beach at low tide and didn't see a single sea slug or any presence of eggs.''
He said there were no signs of egg sacs on the sea grass either, which he described as the "perfect environment'' for the slugs to attach their eggs to.
Dr Walker said sea slug eggs are just as toxic as the slugs themselves, contrary to other reports that the presence of tetrodotoxin would be weaker in the egg sacs.
He said the unit is "really uncertain'' what could be causing the pets to become so ill, but it has "plenty of theories''.
He hasn't ruled out the possibility of slug bait, which he said could be leaching from people's gardens nearby into the storm-water system which discharges onto the beach.
The chemicals in slug bait produce "very similar'' symptoms to those from sea slugs, he said.
Dr Walker said it was possible something was leaking into the storm-water system, which forms puddles on the beach and could be lapped up by dogs. However, he said all possibilities should be examined.
"We are uncertain of what the true cause of the poisoning is, but we want to understand and investigate what the causes are so we can actually inform people, and people can have more certainty around the safety of their dogs and also their children as well,'' he said.
A plan will be made today on how the team might go about discovering what is causing the poisoning, which could include taking water and soil samples, as well as samples from the storm-water system, he said.
But his attempts at finding an answer may be hindered by budget constraints, as he was unsure whether all the necessary tests would be given the go ahead.
"We have to work within a budget ... so those are decisions I can't make,'' he said.
In the meantime, signs have been erected on the beach warning owners of potential poisoning. Owners are advised to keep their dogs on a leash and watch what they eat and drink. If they become ill take them immediately to a veterinary clinic.
