Stephens Lake in Columbia has closed due to an advisory issued by the Missouri Department of Health and Senior Services.
The state has determined there is a risk of harmful algae in the lake.
Signs have been posted at numerous points around the lake notifying park users of the potential presence of harmful algae. Contact with the algae may cause both people and animals to become sick.
If visitors to the park do come into contact with the water, they are advised to wash thoroughly with clean water as soon as possible.
The closure will remain in place until officials determine whether it is safe to reopen. The lake will close for the season on September 30.