PORTER COUNTY, Ind. - The swimming beach at Indiana Dunes State Park reopened Thursday after it was shut down due to an 'unidentified substance' found in the water.

Officials shut down the beach Wednesday afternoon after a lifeguard spotted the contamination.

The beach reopened Thursday because the contamination was no longer visible.

Sample of the unidentified substance have been sent to the Indiana Department of Environmental Management for testing. Officials say those results could take a while to come back.