Panhandle Health officials are urging people to be cautious when swimming, or fishing in the northern portion of Hayden Lake due to a harmful algal bloom.
Algal blooms can produce dangerous bacteria in high concentrations. They can look like an algal mat or murky, or scummy water.
Health officials are asking people who use Hayden Lake for drinking water to be careful, because boiling, or filtering it may not remove the toxins.
They are also urging people who are exposed algae to wash with clean water.