The Canterbury District Health Board (DHB) has issued a health warning after potentially toxic algae was found in the Waikirikiri River at Glentunnel in the Selwyn District.
Photo: 123RF
The DHB said the algae - benthic cyanobacteria - looked like dark brown to black mats, and could produce toxins that were harmful to people and animals.
Canterbury medical officer of health Ramon Pink said people should avoid the river in the Glentunnel area, and keep their pets away until the health warning has been lifted.
Dr Pink said boiling the river water did not remove the toxin.