The chairman of the Senate Judiciary Committee said that scientist Bruce Ivins couldn’t have worked alone in the case of the anthrax letters back in 2001. Patrick J. Leahy said Wednesday that he did not believe the FBI’s supposition that an Army scientist conducted the attacks alone.

Leahy's comments, made as FBI Director Robert Mueller testified before the Judiciary Committee, came as a bomb in the government's case against Ivins and the handling of the seven-year anthrax investigation.

A month ago the FBI and Justice Department said Ivins, an anthrax expert who killed himself in July, was the only one responsible for the deadly mailings. Ivins worked at Army's biodefense lab in Fort Detrick, Maryland and committed suicide on July 29 by taking an acetaminophen overdose.

He had access to the anthrax strain in the letters and might have had reasons to send them to members of Congress and several people from the media. He was FBI’s main suspect. And the case was thought to be over. Leahy did not explain his views, and a spokeswoman did not immediately respond to a request for elaboration.

Leahy asked Mueller about the number of facilities that were capable of producing the strain of anthrax used in the attacks, other than the Army's Dugway Proving Ground in Utah and the Columbus, Ohio, laboratory of Battelle Corp., a CIA contractor. "I do believe there are others," Mueller said. Regarding the FBI’s investigation, he also added: "the steps that were taken in the course of the investigation" were "appropriate ... given the information that we had at that particular time."