Health officials are warning people not to go into a North Canterbury river because of harmful toxic algae.
A water quality scientist from the Canterbury Regional Council says a dog died soon after licking the toxic blooms this week.
Shirley Hayward says warm, dry weather has caused phoridium algae to flourish on the edge of the Ashley River.
Canterbury Medical Officer of Health Alistair Humphrey says the toxins produced by the algal blooms can cause rashes, eye irritation, abdominal pain, vomiting and diarrhoea in humans.
Dr Humphrey says people should stay away from the river and contact a doctor if they experience any symptoms.
The algae is fatal for animals.