A dog has died in Upper Hutt after coming into contact with toxic algae in the Hutt River.

Greater Wellington and Regional Public Health have renewed a health warning after the one-year-old cocker spaniel died shortly after coming into contact with cyanobacteria "mats" on the edge of Hutt River over the weekend.

Dogs were particularly susceptible to cyanobacteria toxins because they liked to scavenge around mats on the river edge.

The warning said river users should avoid contact with the mats of algae, especially making sure children did not touch mats.


The mats could contain toxins which could cause vomiting, diarrhoea and skin irritation in humans.

Thick clumps of the algae, which is brown or black in colour, have been washing up on the river's edge downstream from Birchville.

There was also moderate risk of poisoning from cyanobacteria mats in the Waikanae and Waipoua rivers.

A lack of rain for the past three weeks and warm weather have combined to result in rapid cyanobacteria growth.