Government scientists have opened the anthrax-laden letter sent to Sen. Patrick J. Leahy (D-Vt.) and found it to be "virtually identical" to one mailed to a colleague, Senate Majority Leader Tom Daschle (D-S.D.), the FBI said Thursday.
The disclosure came as scientists continued a painstaking examination of the Leahy envelope and the particles inside it, presumed to be anthrax bacteria, at the Army's biological defense unit at Ft. Detrick, Md.
The FBI said it hopes the letter will provide new information about whoever sent anthrax spores in a series of letters to lawmakers and the news media.
Since Oct. 5, five people have died from anthrax bacteria, suspected of reaching them through contaminated mail. Thirteen others have been sickened.
A senior FBI official, who asked not to be identified, said the Leahy and Daschle letters appeared to be photocopies of an original letter that has not been found.
The FBI said both letters had the same wording. "We have this anthrax," the letters read. "You die now. Are you afraid? Death to America. Death to Israel. Allah is great."
Van Harp, an assistant FBI director and head of the bureau's Washington field office, said the agency will analyze the apparent anthrax bacteria in the Leahy letter in hopes of learning who made it "and how they did it, in order to build a prosecutable case."
A scientist who has been consulting with the government, and who asked not to be identified, said laboratory workers will try to determine the age of the anthrax, which could tie it to material manufactured in biowarfare programs in the former Soviet Union, Iraq or the United States. The U.S. government renounced the use of lethal biological agents in 1969 and stopped making them.
Through sophisticated DNA analysis, it also may be possible to determine the size of the batch from which the anthrax bacteria came. Laboratory workers also may be able to determine the culture medium in which the spores were grown.
The Leahy letter was found Nov. 16 in a large quantity of congressional mail that had been quarantined after the Daschle letter came to light. The letter to Daschle was opened Oct. 14 by an aide, exposing at least 28 people to the potentially deadly bacteria inside.
Initial tests determined that the Leahy letter contained anthrax bacteria similar to that in the Daschle letter. But federal investigators delayed opening the Leahy letter until they could survey outside experts and develop techniques that would protect investigators while preserving the bacteria for analysis.
Harp, in a statement provided by the FBI, described the Leahy letter as being "critically important, because we feel [it] will provide . . . leads to help bring this investigation to a conclusion."
He said it would take weeks to complete the analysis of the apparent bacteria in the letter.
"Because there is a finite amount of material in that letter, it's going to take a very cautious analytical approach," Harp said. "So those tests and examinations will not be completed in the next few days."
Meanwhile, officials said late Thursday that a batch of mail being processed at a special facility in the Federal Reserve courtyard tested positive for anthrax exposure. The extent of the contamination had not yet been determined. A Fed spokeswoman said none of the affected letters had actually been inside Fed headquarters.
Also Thursday, several government agencies announced measures related to the anthrax attacks:
* The inspector general's office at the U.S. Postal Service said it would review the government's methods for decontaminating postal facilities.
Two Washington postal workers have died of inhalation anthrax, likely caused by bacteria that leaked from contaminated letters at postal facilities. Postal workers have complained that the government is not adequately screening and decontaminating mail facilities.
"We're looking at the processes the postal system is using to determine if its facilities are contaminated with anthrax, and if cleanup is adequate," said Sandra Harding, a spokeswoman for the inspector general.
* The Department of Health and Human Services said it was soliciting proposals immediately, and under a speedier approval process, for research into several of the most worrisome diseases that might be spread through bioterrorism. They include anthrax, botulism, plague, smallpox and Ebola-like viruses.
* The Centers for Disease Control and Prevention in Atlanta said Americans who worry about being exposed to anthrax through the mail should not blow on or sniff mail.
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Times staff writers Megan Garvey in Washington and John J. Goldman in New York, and the Associated Press, contributed to this report.