F.B.I. Queries Expert Who Sees Federal Lab Tie in Anthrax Cases

F.B.I. agents yesterday questioned a leading proponent of the theory that the anthrax attacks were the work of someone linked to a federal laboratory or contractor, asking her about possible clues to the culprit's identity.

"They wanted to know whether I had ideas about who did it," said the expert, Barbara Hatch Rosenberg, a molecular biologist at the State University of New York at Purchase and chairwoman of a biological weapons panel at the Federation of American Scientists.

Dr. Rosenberg said that in response she had given the agents detailed information about ideas that she had sketched out in a paper posted on the federation's Web site.

She said the agents had also repeatedly asked her whether she agreed that the perpetrator would have known that anthrax spores would seep through envelopes in which they were mailed. But "I kept disagreeing," she said.

In her paper, Dr. Rosenberg said she believed that the culprit's motive was not necessarily to kill but to stir public fear and so highlight the importance of building up defenses against germ attack.

As the F.B.I. agents consulted Dr. Rosenberg yesterday, a disagreement between federal experts and a former government germ scientist over one narrow issue — how much powdered anthrax was made in 1998 by an Army laboratory at the Dugway Proving Ground in Utah — appeared to be resolved.

Dugway officials had claimed that the amount was small — just grams, or a tiny fraction of a pound. But the scientist, William C. Patrick III, who taught Dugway scientists a secret way to turn wet anthrax into powder, had told military officers that Dugway had made about a pound.

In an interview yesterday, Mr. Patrick said he had meant to say that "we could have produced a pound, not that we did." Quantities of a pound that were made, he added, were not anthrax but Bacillus subtilis, a benign germ sometimes used to simulate anthrax.

Pounds of anthrax, Mr. Patrick said, far exceed what the installation might have needed to test germ defenses, the reason cited by Dugway for making small amounts of anthrax powder.