Investigators say three letters with anthrax similar

WASHINGTON -- Based on handwriting analysis and sophisticated profiling, investigators suspect one person wrote the three letters contaminated with anthrax but have drawn no conclusions about who is behind the attacks, government officials said Friday.

Investigators are exploring a variety of theories, including that a single deranged U.S. resident with a biochemical background, a terrorist group, a foreign country or some combination carried out the attacks, the officials said.

FBI agents are scouring U.S. and foreign laboratories for people who may have had access to the lethal bacteria and were awaiting test results on whether the anthrax in one of the letters was mixed with a chemical to make it more airborne, the officials said.

The officials, all of whom are involved in the investigation, described the current theories of the case on condition of anonymity and cautioned that their descriptions provide only a snapshot.

They said the three letters known to carry anthrax have distinct similarities.

The letters to NBC News anchor Tom Brokaw and the New York Post appear to be photocopies. The formation of the block letters on the third letter, to Senate Majority Leader Tom Daschle, are similar to the letters in the Brokaw and New York Post letters.

However, the Brokaw and Post letters contain some double-writing of the letters "A" and "T" not evident in the Daschle letter, officials noted.

One key to the theory of a single sender is that the block numerals used for the Sept. 11 date on all three letters appear to be near matches.

Investigators also believe the anthrax in all three letters is the same Ames strain that is common to the United States. However, the anthrax in the newspaper's letter was in a heavier, grainier state and the material in Daschle's letter was extremely light and buoyant, they said.