BELOIT, Wis. -

Authorities remain mystified about what was in an envelope dropped off at a Beloit health clinic that prompted dozens of people to be quarantined.

Beloit Police Capt. Vince Sciame said tests Wednesday determined the powder in the envelope was not a biological or a chemical agent. He said authorities don't know what the powder is, so it's being sent to the Wisconsin state crime lab for testing.

Sciame said police talked to the patient who delivered the envelope containing his bill payment to the Beloit Area Community Health Center on Wednesday morning. Sciame said the man told police he didn't put any foreign substance in the envelope.

According to Sciame, the man is "dumbfounded" by what happened.