The beach at Lake Altoona County Park closed Thursday afternoon due to unsafe bacteria levels.
Water testing prompted county officials to close the beach, which already had been under an advisory due to harmful algae blooms.
The Eau Claire City-County Health Department will continue to test water samples and will announce when bacteria levels are within acceptable levels.
Lake Eau Claire remains open, but swimmers are advised to stay away from algae blooms reported there recently.
Other county swimming areas at Big Falls and Coon Fork Lake remain open.