The Christchurch public has been warned to avoid touching dead birds with their bare hands after 300 ducks were found dead due to avian botulism.
The birds may have caught the disease by eating maggots off dead bird carcasses.
Christchurch City Council has issued a warning about the birds and says they will be working to safely remove the carcasses as soon as possible. Avian botulism cannot be transferred to humans.
The council says the toxin which leads to the poisoning, clostridium botulinum, naturally occurs in soils found in ponds and wetlands and it can be harmless until the right environmental factors occur.
The birds, mostly paradise shelducks and some mallards, were found around the Bromley oxidation ponds.
The council says outbreaks of avian botulism are not uncommon worldwide and have occurred in Christchurch previously.
A similar outbreak recently killed at least 50 birds in Te Aroha.