An advisory has been issued by the CRD after water samples taken from Thetis Lake Regional Park have tested positive for blue-green algae and associated cyanotoxins.
CRD say park users should avoid both the upper and lower lakes and to keep animals on a leash to prevent them from drinking or swimming in either lake.
Algal blooms are known toxin producers and can be harmful to both humans and animals.
The algae usually produces a visible blue-green sheen, which appears as surface scum. However, not all blooms are easy to see and toxins can still be present in the water even if you cannot see the algal blooms.
Ingesting water containing the blue-green algae may cause a range of symptoms, including headaches and abdominal pain in humans, and can lead to lethal liver damage in dogs.
The algae advisory at Prior Lake remains in effect.