The toxin linked to the death of dogs on Auckland's eastern beaches has been identified as the deadly poison tetrodotoxin, which attacks the nervous system and can kill within an hour.
Scientists at the Cawthron Institute in Nelson say this is the first time the toxin has been found in this country.
They studied the stomach contents of one of the four dogs that died on the beaches and discovered that the poison in sea slugs is to blame for the death of at least one dog.
Tetrodotoxin is more commonly found in puffer fish, and Cawthron Institute researcher Paul McNabb says it's not clear how it has been getting into sea slugs.
"Sea slugs are consuming something which contains tetrodotoxin and that's killing them. They're washing up on the beach, and dogs are dying from consumption of those sea slugs.
"The mystery is where the tetrodotoxin is coming from in the environment and that's what we're still working on."
The toxin first attacks the nervous system and can kill animals that ingest it within an hour. It can also kill humans within 60 minutes, but people are put off by a putrid odour.
Public health warnings not to swim, gather shellfish or allow children on the beaches remain in place.
