Investigators are looking to see what ships have been passing by a beach along the Indiana lakeshore where swimmers say a slimy chemical has been sticking to their skin.
People at Porter Beach were ordered out of the water Monday, after a strange dark sheen was spotted on the water’s surface.
State environmental officials say tests indicate it’s a chemical known as Tricalcium phosphate, which is used as a food additive and in fertilizers.
A temporary swim ban has been placed at the Indiana Dunes National Lakeshore and the Indiana Dunes State Park.
Investigators are looking at ships because they don’t think the chemical came from the shore.