A spokesman for the institute, Caree Vander Linden, said an earlier review had located all the germ samples listed in the database. But she said some “historical samples” in institute freezers were not in the database, and the new inventory was intended to identify them so they could be recorded and preserved, or destroyed if they no longer had scientific value.

One scientist, who spoke on the condition of anonymity because he was not authorized to comment, said samples from completed projects were not always destroyed, and departing scientists sometimes left behind vials whose contents were unknown to colleagues. He said the Army’s recordkeeping and security were imperfect but better than procedures at most universities, where research on biological pathogens has expanded rapidly since 2001.

The suspension will interrupt dozens of research projects at the institute, whose task is to develop vaccines, drugs and other measures to protect American troops from germ attacks and disease outbreaks. Ms. Vander Linden said some critical experiments involving animals  often used to test vaccines and drugs  would not be halted.

News of the suspension, first reported Monday by the Science magazine blog ScienceInsider, comes as the Justice Department has been interviewing scientists at the Army institute to prepare the government’s legal defense against a lawsuit filed by the family of Robert Stevens, the Florida tabloid photography editor who was the first to die in the 2001 letter attacks.

That lawsuit, filed in 2003 and delayed by the government’s unsuccessful efforts to have it dismissed, accuses officials of failing to assure that anthrax bacteria at Fort Detrick and other government laboratories were securely stored. Dr. Ivins was not suspected in the attacks at that time, but the F.B.I.’s conclusion last year added new weight to the lawsuit’s claims.