Mystery Substance Prompts Closure Of Indiana Beach

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

UPDATE: Glittery Substance That Forced Beach Closure Identified

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 said samples taken of the quarter-mile long slick show it is not.

The Indiana Department of Environmental Management later said the substance was identified as tri-calcium orthophosphate.

Rowe said, around noon Monday, 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 were investigating, including the U.S. Geological Survey.

Rowe said it will likely be sometime Tuesday before they have any idea of what the substance is, so no one is allowed into the water until then.