According to the newspaper, surprised and worried federal investigators said the finding only deepened the mystery about who might be responsible for sending the letters. More than six months after the anthrax letters frightened the nation, investigators are no closer to identifying the source, the Times said.
Previously, investigators believed the anthrax letters sent to Senate Majority leader Tom Daschle, D-North Dakota, and Leahy, D-Vermont, were of equal potency. Each letter was mailed from Trenton, N.J., on Oct. 9, 2001, and each letter contained the same photocopied message.
But subsequent analysis showed that the Leahy letter contained finer, deadlier spores.
Increasingly, investigators have turned to science in a bid to crack the case. They are getting assistance from scores of scientists around the nation, the Times said.