Napier dog owners are being warned not to let their dogs in any freshwater waterways in the city.
Council said while algal blooms might not be as prominent as they are in Anderson Park at the moment, cyanobacteria could still be present.
People were also advised to stay out of Napier's waterways.
Cyanobacteria can be spread through the water, and also through the transfer of bacteria from one waterway to another, for example, through equipment being moved, or a bird such as a duck flying from one waterway to another.
The Environmental Solutions Team is taking samples from different waterways which will be sent to a specialist laboratory to assess levels of toxicity. The results could take a week to be returned but will be released as soon as they become available.
Tidal and saltwater waterways do not appear to be affected at this stage.
Anderson Park was not "full of dead birds", the council said. Many species continued to use the waterways without effect.
NCC staff had also noticed some of the warning signs at Anderson Park have repeatedly been thrown into the water. The council said it would like the behavior to cease.
Owners of dogs registered in Napier who have supplied email addresses will again be contacted via email.
Dog owners should contact a vet immediately if their dogs show the following symptoms after drinking from, swimming or paddling in water: vomiting/being sick, diarrhoea, seizures/fitting, weakness/collapse/unconsciousness, disorientation/confusion, drooling, or breathing difficulties.