Today's discovery came as no surprise to investigators--who say they expected to find traces of anthrax at other mailing facilities--this one inside the Ford Office Building, which handles mail for House Minority Leader Dick Gephardt, among others.
Capitol physician Dr. John Eisold, said, "There is no standing recommendation to expand testing to any other workers other than the workers in that room."
It makes the third location on Capitol Hill which tested positive for anthrax, and the first affecting the House of Representatives.
In Trenton, New Jersey, the source of the letters sent to Senator Tom Daschle and to NBC News, federal investigators were going door to door. So far, they've identified the mailbox where the letters came from, which sent chills through a community not used to the attention.
Bob Dix, a Ewing, New Jersey, resident, said, "It really bothers me. It bothers me a lot because I never thought I would see something like this happen."
But the real clue is the bacteria itself. Although the spores taken from three separate locations all appear to have come from the same batch--it is not as sophisticated as once thought.
Tom Ridge, director of the office of homeland security, said, "The tests show that these strains have not, quote unquote, been weaponized."
The difference is the size of the granules, as demonstrated to Dan Rather by anthrax expert William Patrick.
Weapons-grade anthrax would have been easier to trace. But now investigators may have to expand their search to some labs around the world where unweaponized anthrax is cultured for research. The equivalent, one said, of finding a microscopic needle in a very dangerous haystack.
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