WASHINGTON - Two Defense Department mail handling facilities were shut down on Monday after sensitive detection devices indicated the presence of anthrax but mail at the facilities had already been irradiated to kill any bacteria, Pentagon officials said.
Initial tests at a delivery security facility on the grounds of the Pentagon and at a satellite facility in an office complex several miles away returned preliminary positive results, the Pentagon said. But further tests were negative.
"During routine mail operations, the Pentagon had a positive detection for the presence of anthrax bacteria at the Remote Delivery Facility," the Pentagon said in a statement. "Subsequent tests have proven negative."
"These testing machines are very sensitive and we have had false alarms before. But we take these matters very seriously and are investigating," Defense Department spokesman Glenn Flood told Reuters.
More tests to confirm the results were being conducted at the U.S. Army Research Institute for Infectious Diseases at Ft. Detrick in Frederick, Maryland, said Pentagon spokeswoman Lt. Commander Jane Campbell. The results were expected in two to three days.
The Pentagon said it was working closely with the FBI and the U.S. Postal Service.
About 175 people who normally work at the receiving facility -- designed to check everything coming into the building from letters to packages and construction materials -- were evacuated when the investigation was launched after an alarm was triggered.
The Pentagon said cultures were being taken from workers and they were being offered antibiotic treatment.
Although the receiving facility at the outer edge of the Pentagon was closed, the public post office inside the world's biggest government office building remained open.
Some 3,000 workers in three office towers connected to the Defense Department satellite facility were held inside late into the evening while emergency crews did their work, according to local television reports.
The Pentagon is considered a potential target after the Sept. 11, 2001, attacks on the building and the World Trade Center in New York using hijacked commercial airliners.