Marine deaths stump scientists 

Source: NZPAWarning signs go up on Auckland beaches

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Councils across Auckland are alerting people about the Hauraki Gulf's mystery killer but just what is killing dogs, birds and sea life is still baffling scientists.

By order of public health, signs warn against bringing dogs and kids to popular Mission Bay - and they are up also around eastern beaches all over Auckland.

Experts remain stumped as to what exactly is causing animals to fall ill after two dogs died and more than 30 reports of others getting sick were reported.

"We're still dealing with a fairly toxic chemical and we don't really know what it is... we believe it may be an algal toxin, because this sort of thing has happened in the past," says Dr Denise Barnfather, Medical Officer of Health.

DOC is confident the deaths are not related to 1080 or rat poison recently dropped on Rangitoto Island.

Tests for blue-green algae have been negative and the two dead dogs do not appear to have had any contact with pesticides.

Tests are under way on seaweed in the area. MAF is focusing some of its testing on toxic algae.

"We need to do further work before we would either rule it out of we would bring other potential causes higher up into our consideration," says Naya Brangenberg from MAF Biosecurity.

The Cawthron Institute in Nelson is also helping to investigate the cause.

Scientist Susie Wood says while an algal neurotoxin is believed to be the cause, it could also be something like a new jellyfish species.

She says if algea is the problem, it could easily go away next week, but it could also crop up again.

Wood says algal mats seem to give off an odour which attracts dogs.

And it's not just dogs that have died, other marine life has also perished.

"As you know there's marine life that have also died. Pilchards, penguins and I understand some dolphins as well," says Barnfather.

MAF says there may be a number of things causing the deaths.

It is unclear how long locals will have to stay away from the beach for.

Test results due over the coming days may shed some light, but authorities warn, they may never know what is going on in the Hauraki Gulf.

For now the basic message is this - avoid all contact with the sea on Auckland's eastern shores.