People should not be using water from Lake Rosalind near Hanover as a drinking water source.
Tests have confirmed there are toxins in the water from blue-green algae. Earlier this month the Environment Ministry tested the waters after the algae was found. The results came back positive for toxins.
The Grey Bruce Health Unit's Bob Hart says people should take precautions.
"If anyone is actually drawing water from the lake and using it as a drinking water supply or for bathing or showering they shouldn't be doing that. Pets should be excluded from the water as well as people swimming in it and fish should not be consumed from the water as well," says Hart.
Hart says the precautions around Lake Rosalind water will last well into the fall and includes water from Marl Lake connected to Lake Rosalind. He says people on wells near the lake have nothing to worry about.