The U.S. Army has halted research on most germs at the same biodefense lab fingered as the source of the deadly 2001 anthrax mailings, after discovering that some of the pathogens stored in its refrigerators and freezers aren’t listed in its database.

Col. John P. Skvorak, commander of the Army Medical Research Institute of Infectious Diseases at Fort Detrick in Maryland, ordered the suspension Friday. The shutdown could last up to three months as investigators attempt to get to the bottom of the questionable inventory, and will affect "most or much" of the research projects at the lab, where government scientists study drugs and vaccines that could be used to make biological weapons, a lab spokesperson, Caree Vander Linden, tells The blog ScienceInsider was the first to report the story and yesterday posted the memo from Skvorak ordering the review.

Fort Detrick scientist Bruce Ivins apparently committed suicide in July as the FBI was reportedly set to arrest him for allegedly sending anthrax spores through the mail, attacks that in 2001 killed five people and sickened 17 others.

In the wake of the attacks, officials tightened record-keeping requirements at government labs and, during a recent review, inspectors uncovered some germ samples at Fort Detrick that were not registered in its database. Officials want to identify and record them – or destroy them if they’re not needed for study, Vander Linden says. Ongoing animal studies and care will continue during the review, she adds.

In the past, viruses, bacteria and toxins referred to as biological select agents and toxin (BSAT) haven’t shown up in the lab’s database “due to accounting errors, transcription errors, or BSAT that had not been reassigned when an employee left the institute,” Skvorak noted in the memo. “I believe that the probability that there are additional vials of BSAT not captured in our … database is high.”

We’ve got more on the clues that led to Ivins being suspected in the anthrax attacks and why investigators didn’t zero in on him until they determined the spores had not been weaponized.* You can also read about the original anthrax suspect, Steven Hatfill, who’s since been exonerated.

Image of Bacillus anthracis/CDC

* Erratum (2/1209): The original sentence stated that the investigators determined the spores had been weaponized.