The deaths of yellow-eyed penguins on Otago Peninsula are still being investigated. Fifty-six penguins have been found dead in the past month.
The Department of Conservation started finding them at breeding sites during annual nest checks.
DoC said water samples have collected for testing for possible toxins.
Biodiversity programme manager David Agnew said the situation is extremely puzzling as no other wildlife appear to be affected and every test so far has been inconclusive.
Mr Agnew said there have been no further deaths over the past few days.