Environmental scientists with the Kentucky Division of Water are taking samples of the Ohio River to see if the advisory can be lifted for the blooming algae problem.
The advisory was issued for recreational use in September.
The drinking water is considered safe.
Louisville has an Ironman event scheduled for Sunday.
Organizers say the swim portion of the Triathlon will be canceled if the advisory remains in effect.
Blue-green algae occur naturally in the environment, but harmful algal blooms occur when there are excess nutrients, sunny conditions, warm temperatures, and conditions of low-flow or low-water.
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