Staff file photo by Sam Yu In this September 2003 file photo, Bruce Ivins is seen at the American Red Cross Emergency Shelter in the Frederick Community College gym.

Ivins, a Fort Detrick anthrax researcher and the FBI's only suspect in the 2001 anthrax mailings, stated in a July 9 group therapy session that he planned to kill coworkers and others who had wronged him. He died July 29 after apparently committing suicide.

In the affidavits supporting the requests for warrants, FBI Special Agent Marlo Arrendondo states that on July 24, FBI agents observed Ivins using the two computers at the C. Burr Artz Public Library to access e-mail accounts and view websites dedicated to the anthrax investigation.

A Department of Justice spokesman declined to comment on why the FBI waited a week after observing Ivins use the computers to seize them, and why it waited another week before obtaining the search warrants.

Elizabeth Cromwell, the library's public relations manager, said the FBI hasn't told the library when it might return the computers.

The Department of Justice released the warrants the day after releasing a stack of other affidavits and search warrants outlining the government's case accusing Ivins of the 2001 anthrax mailings that left five people dead and hospitalized more than a dozen.

In the documents, the FBI said Ivins 1.) had control of a flask of anthrax that shared characteristics with the bacteria used in the letters, 2.) could not adequately explain why he was doing lab work late at night and on weekends in the days before the letters were mailed, and 3.) was suffering from mental health problems in the months preceding the mailings, among other reasons.

Department of Justice officials said Wednesday their case against Ivins was strong, although they admit they can neither place Ivins in Princeton, N.J., where the letters were mailed, at the appropriate time, nor prove the handwriting on the envelopes and letters was his.

In an e-mailed statement, Paul Kemp, Ivins' attorney, blasted the Justice Department's documents and press conference as "an orchestrated dance of carefully worded statements, heaps of innuendo and a staggering lack of real evidence -- all contorted to create the illusion of guilt by Dr. Ivins."

Russell Byrne, who worked with Ivins in the bacteriology division at the U.S. Army Medical Research Institute of Infectious Diseases, said he still believes Ivins was innocent.

Byrne said that while Ivins had cause to be tense, he never saw him exhibit the sort of paranoid behavior described in the FBI affidavits.

Lawmakers, including Rep. Rush Holt, D-N.J., and Sen. Chuck Grassley, R-Iowa, have criticized the FBI, calling its handling of the case sloppy, and called for Congressional hearings into the investigation.

The evidence the Justice Department has released thus far isn't conclusive, said Michael Stebbins, a geneticist who runs the Federation of American Scientists' biosecurity project.

Stebbins said he wants to see the actual evidence the FBI had, rather than affidavits, and he said he particularly wants to see the evidence linking the anthrax used in the mailings to the anthrax to which Ivins had access.

Maryland Democratic Sen. Benjamin Cardin said he's pleased that the Justice Department has released information on the case, and is hoping that more will be released.

Although the Army has issued new regulations governing access to deadly diseases and the labs where they're studied, Congress needs to take a closer look at the issue, he said.

Through a spokeswoman, Rep. Roscoe Bartlett, R-District 6, said he had not reviewed the documents the Department of Justice released Wednesday, and was not seeking to be briefed on the case.

"In any event, as a scientist and engineer and a conservative, (Bartlett) would be unlikely to base a decision about appropriate Congressional responses soley (sic) on materials about the case against Dr. Ivins released by only one relevent (sic) federal agency, in this case, the DOJ," Bartlett spokeswoman Lisa Wright wrote in an e-mail.

Through a spokeswoman, Democratic Sen. Barbara Mikulski declined to comment citing the ongoing investigation.

Regardless of what other information the FBI releases, Stebbins said even if one accepts the premise that Ivins did send the letters, it's not clear what could be done to stop something similar from happening in the future.

"This is something that happens in our society ... People break down," he said. "I don't know of any measures that could be taken to prevent that from happening, short of draconian screening of people over and over and over again."

Staff writer Gina Gallucci-White contributed to this article.