The appearance of a strange blue-green substance has prompted the Napier City Council to warn owners to keep their dogs away from the waterways in Anderson Park.
The council environmental team are inspecting the odd substance, which "could be" cyanobacteria bacteria, often found growing on greenhouse glass, or around sinks and drains.
If it is cyanobacteria, it could be potentially fatal to dogs.
While tests are being conducted, a vacuum truck is being used to remove as much of the substance as possible.
Test results should be revealed this morning and warning signs have been placed around the affected area.