Experts have added a grim warning to the poison beach scare in Auckland, saying the toxin that killed dogs is deadly enough to paralyse humans in seconds and kill them within an hour.
Test results have shown that tetrodotoxin, a poison found in puffer fish, is responsible for the deaths of two dogs, birds and sealife on Auckland beaches.
The poison was found in the dead dogs' vomit and in a sea slug sample taken from Narrow Neck Beach on the North Shore.
Further tests are being carried out to find out how the sea slug came to contain the poison.
Touching a dead animal on the beach could be enough to endanger human life, said Cawthron Institute algae specialist Paul McNabb.
He said that warnings for people to keep away from beaches were not extreme, because of the effects the toxins had on humans.
"People can die from this," Mr McNabb said.
"If you put a slug in your mouth, you'd be vomiting and your entire body would be tingling.
"Within minutes you'd be paralysed. Your heart and lungs would shut down and you'd be dead within the hour.
"Or if you touched it and it was all over your hands and you went and ate a sandwich ..."
Mr McNabb said anyone who came down with symptoms including vomiting and drowsiness, after being at a beach, should see a doctor.
But the only way a person would die was if they consumed the poison.
Health authorities were alerted to the problem when several dog owners reported their pets getting sick, vomiting and foaming at the mouth, after walking on an Auckland beach.
Warning signs were soon posted at beaches on the North Shore and in Auckland City after more reports of pets becoming sick and birds and fish washing up dead on beaches.
Up to eight agencies - including health authorities and city councils - have been meeting to examine the test results.
Mr McNabb said it was a sad but thankful thing to have been alerted to the problem following the dogs' deaths.
"It's good that it's happened like this," he said.
"It's sad for the dogs and their owners - but it's better to have it happen this way and we find out from the dogs dying and not from people dying."
Auckland Regional Public Health officials said tests were still being conducted.
Until the investigating agencies were sure it was safe for people and their pets to be on the beaches, the warnings would not be lifted.
* Beach poison Q&A
Who is involved?
Auckland Regional Council, MAF Biosecurity, Auckland Regional Public Health Service, Department of Conservation, North Shore City Council, Manukau City Council, Auckland City Council, and Rodney District Council.
Why so many?
City and district councils have coastlines bordering the Hauraki Gulf.
Auckland Regional Council is responsible for water quality and the coastal marine area. Has been co-ordinating the public comments.
Department of Conservation monitors the deaths of little blue penguins and other marine animals.
MAF Biosecurity is co-ordinating the scientific tests on dead animals.
Auckland Regional Public Health Service assesses the threat to human health and issues health warnings.
Sea slugs: The only toxic thing found on the beach where at least two of the four dogs died. Toxins in the slugs, believed to have come from tropical puffer fish, were found to match toxins found in the dogs' vomit.
Deliberate poisoning: An early theory but authorities began to suspect a natural toxin when dog illnesses were reported from far-apart beaches on the Hauraki Gulf.
Toxic algae: The prime suspect last week, but tests on water from North Shore beaches and dog vomit did not show any well-known species of toxic algae.
Brodifacoum/1080: A popular theory among Herald readers. The rat poison dropped on Rangitoto and Motutapu islands in recent weeks by the Department of Conservation was Brodifacoum, a slow-acting poison that causes internal bleeding. University scientists say there is no evidence of internal bleeding in wildlife, and MAF biosecurity found no evidence in dogs.
Pilchard virus: Struck in the 1990s and could explain large numbers of pilchards washing up.
Seaweed, jellyfish: Being tested.
Why has it taken so long?
An Auckland Regional Council official said the reason for delays was the time taken for scientific tests, although they were being done more quickly than usual. "Testing like this doesn't happen instantly like it does on TV."
More tests on wildlife will be carried out this week.