Dr. Na-Koshie Lamptey says swimming, water-skiing and contact with water should be avoided if the water is discoloured or there is surface scum.
She says water from a lake should not be used for drinking or cooking without treatment, adding that boiling water from a lake with a bloom will not remove the toxins.
Laboratory tests of samples taken in different areas at Harvey Lake confirmed the presence of blue-green algae, or cyanobacteria (Sigh-AN-oh-bacteria).
Blue-green algae can produce toxins which can cause skin, eye and throat irritation as well as gastrointestinal illness, if consumed.
The Health Department says young children and those with skin conditions may be particularly vulnerable to the effects, while blue-green algae can be fatal to pets and livestock.