Thetis Lake (Photo by Ryan Holder/Instagram)

The CRD has issued a warning against swimming or allowing pets to swim in Thetis Lake after toxic blue-green algae was detected in the water.

Island Health has recently documented a visible blue-green algae bloom at Thetis Lake, known to produce cyanotoxins.

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 them.

Ingesting water containing the algae may cause a range of symptoms, including headaches and abdominal pain in humans, and can lead to lethal liver damage in dogs.