CHICAGO (CBS) — Indiana environmental officials were investigating whether a Porter County manufacturer was responsible for a slick of glittery material that kept many swimmers out of Lake Michigan in northwest Indiana on Monday.

“The material that was found in Lake Michigan yesterday, we do know that it’s tri-calcium orthophosphate,” said Dan Goldblatt, spokesman for the Indiana Department of Environmental Management, who added the test results are preliminary.

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Swimmers in Lake Michigan along Porter Beach and other parts of northwest Indiana were ordered out of the water on Monday after several people ended up covered in the glittery substance.

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WBBM Newsradio’s Mike Krauser reports the substance does not appear to be dangerous.

“That’s produced for a lot of things,” Goldblatt said, “One thing that it’s used for is actually a food additive, and there is a plant nearby in Porter County that produces the stuff and ships it in large quantities in barges across the lake.”

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The chemical is also used in some fertilizers.

Goldblatt said the slick spotted in Lake Michigan has not been tied to the company, which he did not name.

“We don’t have confirmation that’s where it came from. They do make the material, and we do know that that is what was found in the lake,” Goldblatt said.

It’s unclear whether it was spilled into the lake from a barge, or carried in the air.

A swim advisory is in effect.

Officials were trying to determine if it is the same glittery material that was carried through the air and landed recently in a section of Hammond.

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Residents in Hammond had complained about a black and silver glittery substance in their yards, and authorities initially believed it was kish graphite – a particle common in the steelmaking process – from nearby steel mills, but have determined that was not the case.