Alberta Health Services has issued a blue-green algae warning for Lake Isle northwest of Edmonton.
People visiting the lake are advised not to drink the water, eat fish, swim or wade in the lake and avoid contact with any algae along the shore.
They are also advised to keep their pets away from the water.
Blue-green algae produce a toxin that can make humans and animals sick, and cause liver damage over time in those who use the lake for drinking water.
The toxin can stay in the lake after the algae have moved or disappeared.
The advisory will stay in effect until further notice.
Lake Isle is about 85 kilometres west of Edmonton.