The inquiry begun in 2008 by the service's Criminal Investigation Command is "in the final stages of its mandatory review process before being closed," according to command spokesman Christopher Grey. There is "no evidence to date of any criminality related to the unaccounted-for items," he said.
The Venezuelan equine encephalitis virus is considered a possible tool of bioterrorism, but poses a significantly smaller threat than anthrax and other disease agents handled at the institute.
The missing material is believed to have been destroyed when a freezer malfunctioned, said USAMRIID spokeswoman Caree Vander Linden. The absence was detected last year by a scientist conducting an inventory of samples that had been passed down by two other researchers upon their successive departures from the facility.
"We'll probably never know exactly what happened," said one Army official. "It could be the freezer malfunction. It could be they never existed."
Investigators spoke with "literally hundreds of people" in the course of their work, the official said.
"They caught me on my cell phone on the road, and I stopped and talked to them for quite a long time," said former laboratory scientist Alan Schmaljohn, who now teaches at the University of Maryland. "She was just going down this whole list of questions, including, 'Did you take it?'"
Schmaljohn answered in the negative. It would not be hard to lose three vials, particularly if they must be rearranged following a problem with a freezer, he said.
