An envelope with an Eau Claire postmark caused an eastern Wisconsin county courthouse to be locked down.
When the Brown County clerk of courts opened the envelope yesterday afternoon, a suspicious white powder fell out.
A hazardous materials crews was called in and officers sequestered 20 employees in case of contamination
Investigators don't think the powder is anthrax because the Eau Claire post office has machines that can detect it.
But, samples will still be analyzed.