This website describes the FBI's actions in response to the anthrax scare on Capitol Hill. From the website, "A letter addressed to Senator Patrick Leahy was found by FBI and Environmental Protection Agency (EPA) hazardous materials personnel on Friday, November 16. The letter was in one of the 280 barrels of unopened mail collected from Capitol Hill after an anthrax-contaminated letter to Senator Daschle was first discovered. An innovative protocol was developed by scientific and forensic experts to analyze these congressional mail bags for anthrax contamination. The new method eliminated the need for hazardous materials teams to sift through each piece of mail in the 635 trash bags to find additional contaminated mail."
Federal Bureau of Investigation: http://www.fbi.gov