WASHINGTON -- An apparent mix-up at a laboratory is being blamed for the anthrax scare that closed three mail facilities handling Pentagon-bound mail and prompted nearly 900 workers to receive antibiotics.
The two-day scare turned out to be a false alarm after definitive tests at two facilities came back negative Tuesday for the deadly spores.
Officials believe the confusion stemmed from a mistake at the laboratory that did the initial testing, and the mistaken conclusion was confirmed by a Defense Department laboratory at Fort Detrick, Md.
The working theory is that workers at the initial laboratory -- Commonwealth Biotechnology Inc. in Richmond, Va. -- contaminated the sample taken from the Pentagon with anthrax that is kept on hand for comparison purposes, a Homeland Security official said yesterday, speaking on condition of anonymity. That would explain why the sample came back as positive for anthrax.
That initial sample, possibly already contaminated, was then delivered to Fort Detrick, which confirmed the presence of anthrax. ''It had already been handled by the contractor," said Caree Vander Linden, spokeswoman for the US Army Medical Research Institute of Infectious Diseases at Fort Detrick.
Later tests proved negative, and officials realized the initial error, officials said.
Robert Harris, chief operating officer of Commonwealth Biotechnology, said it is premature to conclude that there was contamination at his lab and said testing is ongoing.
''The issue of contamination is questionable," he said. He said he still believes that the original sample might have been ''a true positive sample" for anthrax. ''That's a possibility at this point," he said.
Harris said his company does daily testing on swabs taken from filters at the Pentagon mail facility.
Warning signs at the two Pentagon mail facilities led to the comprehensive testing Monday. Nearly 900 workers were given antibiotics, and officials closed three mail facilities, including two that serve the Pentagon.
In 2001 anthrax-by-mail attacks killed five people and panicked Americans still raw from the attacks of Sept. 11, 2001. Since then, scores of initial tests in government mailrooms have falsely reported anthrax.