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PORTER, Ind. (AP) -- Indiana officials say a substance found floating on Lake Michigan that led to beach closures is made at a nearby plant shipped out on barges.

Indiana Department of Environmental Management spokesman Dan Goldblatt told The Times of Munster (http://bit.ly/15hJz1p) on Tuesday that preliminary tests showed the substance is tricalcium orthophosphate, an anti-caking agent used as a food additive and in industrial applications.

Goldblatt didn't identify the Porter plant but says it ships it out of the nearby Port of Indiana. He says the U.S. Coast Guard officials believe the material in the lake originated on a boat or a barge,

Goldblatt says it's not known if the concentrations found in the water caused any health threats.

Beaches were closed Monday after people reported being covered by the substance.
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PORTER, Ind. (ABC NEWS) -- Several beaches in northwest Indiana remain closed for swimming Tuesday
after a substance was found in the water.

Investigators are trying to identify the substance that showed up in the water Monday.

A dark, slimy substance snaked its way through the southern tip of Lake Michigan- but on Monday, experts said the substances seen streaming into the lake are considered normal from erosion and storms.

So far, the Indiana Department of Environmental Management and the US Geological Survey have ruled out an oil spill. Preliminary tests show "metallic flakes" and authorities said most of it is harmless. However, they added that it's not clear what else is in the substance.

"There was a silvery, sticky material that was literally sticking to kids as they came out of the water. So they called 911, and national rangers responded and at that point they closed the water," said Bruce Rowe, a park ranger with the National Park Service.

Officials then ordered swimmers at Porter Beach and the Indiana Dunes State Park out of the water. The unknown substance has closed other beaches from Porter to Michigan City, as well.

Rowe is anxiously awaiting rest results Tuesday morning as he informs people at the Visitors Center about the problem.

"We stoppeda the Visitors Center trying to find beach spots and they told us we're not allowed in the water," said Syahirah Aziz, a disappointed visitor.

As a precaution, Indiana conservation officers are asking people to stay out of the water until they can determine what the substance is.

A group of environmentalists who were coincidentally working on another project in the area are scratching their heads

"It is disappointing but without knowing what it is there is no one to blame yet," said Nicole Messacar, LaPorte County Soil and Water Education District.

Meanwhile, authorities say it may be a substance from a nearby industry. The Times of Northwest Indiana reports that a spokesman for the Indiana Department of Environmental Management has said the substance is tricalcium
orthophosphate, which is used as a food additive and in industrial applications.

The report also says that an unidentified Porter plant manufactures the material and ships it out of the Port of Indiana on barges.

However, official test results are expected to be released later on Tuesday.