Officials at Lake Macbride State Park are warning people to stay out of the water.
The Iowa City Press-Citizen says the warning comes after officials found higher toxin levels in the water last week. The say the levels showed blue-green algae.
Swimmers who accidentally swallow water or accidentally breathe in the algae can get sick. Symptoms include nausea, vomiting, asthma-like symptoms, and several others.
Park leaders tested the water again this Tuesday, but won't know the results until tomorrow.