An inventory of potentially deadly pathogens at Fort Detrick's infectious disease laboratory found more than 9,000 vials that had not been accounted for, Army officials said yesterday, raising concerns that officials wouldn't know whether dangerous toxins were missing. After four months of searching about 335 freezers and refrigerators at the U.S. Army Medical Research Institute of Infectious Diseases in Frederick, investigators found 9,220 samples that hadn't been included in a database of about 66,000 items listed as of February, said Col. Mark Kortepeter, the institute's deputy commander. The vials contained some dangerous pathogens, among them the Ebola virus, anthrax bacteria and botulinum toxin, and less lethal agents such as Venezuelan equine encephalitis virus and the bacterium that causes tularemia. Most of them, forgotten inside freezer drawers, hadn't been used in years or even decades. Officials said some serum samples from hemorrhagic fever patients dated to the Korean War. The overstock and the previous inaccuracy of the database raised the possibility that someone could have taken a sample outside the lab with no way for officials to know something was missing. The institute has been under pressure to tighten security in the wake of the 2001 anthrax attacks, which killed five people and sickened 17. FBI investigators say they think the anthrax strain used in the attacks originated at the Army lab, and its prime suspect, Bruce E. Ivins, researched anthrax there. Ivins committed suicide last year during an investigation into his activities.