FBI searches scientist's home in anthrax probe

FBI and Postal Service agents conducted a second search of the apartment of former Army researcher Steven Hatfill.

FORT DETRICK, Maryland (CNN) -- The FBI on Friday sifted through documents and other materials gathered from the Maryland home of a former government researcher under scrutiny in the anthrax investigation.

Law enforcement sources say materials are being tested and evaluated following Thursday's search of Steven Hatfill's apartment near the U.S. Army biowarfare defense lab in Fort Detrick, where he once worked.

FBI agents have interviewed 500 people and issued 1,700 grand jury subpoenas as part of the investigation. But no one has been arrested in the attacks last fall which killed five people.

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Meanwhile, Hatfill's current employer, Louisiana State University, on Friday placed him on paid administrative leave for one month.

"His status will be re-evaluated at the end of that period," LSU said in a statement.

The university hired Hatfill on July 1 to be the associate director of the school's National Center for Biomedical Research and Training, a program funded by the U.S. Justice Department.

Sources note that while Hatfill is one focus of the anthrax investigation, 20 to 30 other individuals also are under scrutiny, part of a rotating short list.

Thursday's search was the second time agents have searched Hatfill's apartment. FBI agents also searched a friend's apartment and a storage facility that Hatfill uses in Florida.

The U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick has been a focus of the FBI investigation because workers there did experiments with anthrax.