A restroom at a Walmart in Muncie, Indiana, has been closed indefinitely after an employee discovered a working meth lab inside.

According to police, the employee became suspicious after seeing a man enter the restroom Thursday night with a backpack and leave without it.

Police examined the backpack and determined that it was a miniature, active meth lab, containing the materials used to cook meth by the "shake and bake" or "one-pot" method.

The mixing of such chemicals runs a high risk of explosion or contamination.

Indiana State Police released a statement, saying "Rather than the meth cook blowing up or contaminating their house, they are now often leaving behind the deadly explosive chemicals in public places to return later to get the finished product. They will often times dump their trash, which includes Sudafed blister packs, Liquid Fire drain cleaner bottles, battery casings, and plastic drink bottles with white residue in the bottom, in rural or desolate areas, or in alleys or vacant lots."

Members of the state police meth suppression team removed the dangerous chemicals.

That men's restroom and the nearby women's restroom were closed by health department inspectors until they can be decontaminated by a professional cleaning firm.

An investigation into who left the backpack in the restroom is under way.

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