• Swimmers have been ordered out of Lake Michigan at Porter Beach because of a substance in the water. WBBM's Nancy Harty has more.

    It was originally thought to be an oil slick that prompted the closure of Porter Beach and the Indiana Dunes State Park Beach right next door, but park ranger Bruce Rowe says samples taken of the quarter-mile long slick show it is not.

    "The initial results, very initial, are that it is not oil based, but that we don't have the specific results as to what it is," Rowe says.

    Rowe says that around noon, beach visitors noticed their children coming out of the lake with a silvery, almost metallic material sticking to them, which prompted the beach closure.

    Lifeguards walked the shoreline, announcing the water was off-limits.

    "They said it with urgency. They told everybody to evacuate the water immediately," beachgoer Jason Pavela said.

    Several agencies are investigating, including the U.S. Geological Survey. Rowe says it will likely be the morning before they have any idea of what the substance is, so no one is allowed into the water until then.