How long has this mine been closed? How long has there been suspicion that there was a major problem? So what triggered this sudden emergency announcement?
http://www.epa.gov/region8/superfund/libby/background.html
Libby History
Gold miners discovered vermiculite in Libby in 1881; in the 1920s the Zonolite Company formed and began mining the vermiculite. In 1963, W.R. Grace bought the Zonolite mining operations. The mine closed in 1990.