The Beloit Police Department has ended its investigation into an envelope dropped off at a health clinic that prompted dozens to be quarantined and sent 15 people to the hospital as a precaution.
Fire Chief Brad Liggett said no substance was found when officials tested the envelope, bill, check and the work area.
Capt. Vince Sciame said officials tested the envelope, bill, check and the desk it touched for dangerous residue but found nothing chemical or biological. He said there was a very small amount of whatever was inside.
Sciame said the man who dropped off his bill and payment Wednesday morning at the Beloit Area Community Health Center was forthcoming and said he didn't put anything else in the envelope.
Beloit police said team testing the substance advised it was confident in the test results that there was no danger to the community and no further analysis would be completed on the envelope and its contents.
He said the investigation is considered closed. He said it's possible they will never know.
Police said the substance is considered unknown and the symptoms felt by three employees are unexplainable.
"The positive news is that no one was seriously injured in this incident," Liggett said.