Deadly porcupine fish are being tested after washing up on a beach near Wellington.
Up to 15 fish were found washed up dead at Petone Beach in Lower Hutt on Wednesday.
Fish collection manager at Te Papa museum, Andrew Stuart, says porcupine fish are closely related to puffer fish and are similarly poisonous.
They should not be eaten or fed to animals.
The fish have been sent to the Cawthron Institute in Nelson for tests to find out what caused them to wash up dead.
In Auckland, a suspected toxin is believed to be responsible for the deaths of several dogs and various marine life at eastern beaches.
Last week, scientists discovered sea slugs containing tetrodotoxin, a deadly substance also found in puffer fish.
The Hutt City Council is advising people to exercise caution until the council knows what it is dealing with.