Emergency officials converge at Porter Beach in Northwest Indiana Monday when a mysterious substance was discovered in the water. (CBS)

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.

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.