A toxic algae in Mosgiel's Silver Stream is believed to have killed two dogs and people are being warned to keep their pets clear of the river.
Otago Regional Council says the black, shiny algae, phormidium, is regularly found in Otago in summer as it likes high temperature and low river flows.
It says says the algae can also cause allergic reactions in humans like eye irritations, rashes, stomach cramps and diarrhoea.
The council says people should supervise small children close to Silver Stream to ensure they don't eat or touch any algae.
