A health warning has been issued for the Selwyn River in Canterbury after potentially toxic blue-green algae was found at the Whitecliffs Domain.
Medical Officer of Health Ramon Pink says the algae resembles dark brown to black mats.
Dr Pink says contact with the algae can cause rashes, nausea, stomach cramps, and tingling and numbness around the mouth and fingertips in people. It is also poisonous to animals.
He says people should stay out of the water and refrain from drinking it, even after boiling, as that does not remove the toxin.
Dr Pink says if people have any of the symptoms after contact with water they should contact their doctor immediately, and take any animals in distress to the vet.
