The North Bay Parry Sound District Health Unit says two sightings of blue-green algae in Callander Bay have been reported this month, with the most recent sighting reported to the Ministry of Environment, Conservation and Parks on August 20.
Officials say sampling done by the ministry has confirmed the presence of harmful blue-green algae.
The Health Unit is advising residents and visitors of Callander Bay to use caution when using the lake water.
They add there is a risk that harmful toxins can be produced by blue-green algae.
Officials say toxins can stay in the water for up to three weeks after the algae bloom is gone, causing skin irritation, and if swallowed, diarrhea and vomiting.
