BELOIT, Wis. (AP) – 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.  Capt. Vince Sciame says officials tested the envelope, bill, check and the desk it touched for dangerous residue but found nothing chemical or biological. He says there was a very small amount of whatever was inside.  Sciame says the man who dropped off his bill and payment Wednesday morning at the Beloit Area Community Health Center was forthcoming and says he didn’t put anything else in the envelope.   Sciame says the state’s crime lab is doing more tests. He says the investigation is considered closed pending those results. He says it’s possible they will never know.