Toxic sea slugs could be responsible for the deaths of two dogs
on North Shore beaches.
Scientists from Nelson's Cawthron Institute have found the dogs died because they ate something poisonous.
It said the scientists were still trying to find out what the toxic substance was, but suspected sea slugs which are known to feed on toxic algae that grows on the sea floor could be responsible.
Four toxic sea slugs had been found washed up on Narrow Neck beach, where one of the dogs died, the report said.
Paul McNabb from the Cawthron Institute says results have found that the dogs ate something toxic, rather than getting sick from walking on the beach, or being in contact with the sea water.
Tests were done on a number of the sea slugs scattered
along the beach.and they were found to be toxic.
Chemist Paul McNabb says the dogs vomit was very toxic, and they had probably eaten the slugs.
He says it is likely the algae is also responsible for killing a number of penguins, dolphins and pilchards.
Auckland Regional Public Health Service has warned people to avoid contact with sea water and sea life around the Hauraki Gulf.
It has also warned against taking children and pets to the beaches, and that fishing, swimming and diving should cease.
Collecting fish and shellfish has also been advised against.
There were also hundreds of fish, some penguins and five dolphins reported to have suffered mysterious deaths .
North Shore City Council environmental health team leader Duffy Visser said she had yet to receive any test results and all the warnings were still in place.