It's probably nothing, but Utah's Dugway Proving Ground — where the Army tests biological weapon defense systems — is on lockdown and no one can leave. "We are working [...] to resolve a serious concern within the Test Area." (Updated)
Via ksl.com, a statement from Dugway Proving Ground:
Wednesday, "during a routine inventory of sensitive material in the chemical laboratory, Dugway officials discovered a discrepancy between the records and the agent on-hand. As a precaution, the commander immediately locked down the installation and began efforts to identify the cause of the discrepancy.
Inventories showed a discrepancy of less than 1 ml (less than one-fourth of a teaspoon) of VX "nerve agent."
The vial with 1 ml was located at 3 a.m. All personnel are uninjured and safe. The public is safe as well.
VX is an amber colored, odorless, tasteless oily liquid that does not evaporate easily unless temperatures are high. It evaporates very slowly, almost like motor oil. People can be exposed through skin contact (the most toxic way), eye contact or inhalation. It affects the body's ability to carry messages through the nerves."
Don't worry — they just misplaced a little VX for a while, that's all.