Grey side-gilled sea slugs found in Pilot Bay are the same species as those attributed to the 2009 dog deaths.
"It's a new risk," said Dr Jim Miller, medical health officer at Toi Te Ora - Public Health Service. "It's another thing for people to look out for."
While the sea slugs
have been seen in the water, there have been no reports of their presence on land.
Rob Donald, of the Bay of Plenty Regional Council, said the sea slugs become a risk when they start to wash up on beaches.
He said the main risk came from direct physical contact with the slugs.
The toxin poses the most serious threat when ingested so the greatest risk is to pets and unsupervised children.
"You'd have to actually pick one up and put it in your mouth. The advice is not to touch them," he said.
Their toxin, tetrodotoxin, can be highly dangerous.
"It's a toxin that affects your nervous system - so not the sort of thing you should be handling," Dr Miller said
Information on the Niwa website says the toxin from the sea slugs can be lethal even in small doses. They estimate that "probably half a teaspoon of sea slug" could kill a human.
While the sea slugs were found in Pilot Bay, Mr Donald said they could potentially be found elsewhere.
"They could be found anywhere in the harbour."
The Tauranga discovery was made by scientists in 5-6m of water directly offshore as part of a nationwide scientific survey two weeks ago.
It is not known whether all of the slugs are toxic or whether they are only toxic in the North Shore and Coromandel areas.
If a sea slug is discovered on land it should not be touched. Call Toi Te Ora health protection officer on 0800 221 555, then press 7.
