The home of a former Army scientist considered a "person of interest" in the investigation of last fall's anthrax attacks has been searched for a second time by FBI and Postal Service agents.

But investigators still refuse to label the researcher, Steven J. Hatfill, a suspect in the case.

The FBI gained a search warrant Thursday to look inside Hatfill's residence at Detrick Plaza Apartments in Frederick, Md., according to two U.S. government officials who spoke on condition of anonymity. Hatfill consented to the first FBI search on June 25 and no warrant was needed.

Federal agents also searched trash bins outside Hatfill's apartment. A dark blue van was parked nearby with its back doors open and white cardboard boxes sat next to the bins.

Agents also searched a self-storage unit in Ocala, Fla., that Hatfill used, one official said. The unit also was searched in June.

It was unclear whether the FBI contacted Hatfill before gaining the warrant to search his home.

Hatfill keeps a residence at the apartment building, but has not lived there since the first search, according to neighbors.

FBI Director Robert Mueller declined to say why a second search was conducted.

``We're making progress in the case but I can't comment on ongoing aspects of the investigation,'' he said.

Hatfill, 48, was not questioned and no arrests in the case are imminent, a government official said.

Five people were killed in last fall's anthrax mailings. Federal investigators did talk to Hatfill about the case when his name first surfaced last winter, but no details of the interview have been disclosed.

Several phone calls to Hatfill's attorney, Thomas C. Carter, were not returned. But in a phone interview with WJZ-TV of Baltimore, Carter said Hatfill has done nothing wrong.

``He is one of many scientists who are undergoing the same scrutiny by the authorities, but for some reason, his name keeps popping up,'' Carter said. ``But he's a patriot — he's going to continue to cooperate in every way.''

During the first search, FBI agents, some in protective clothing, removed computer components and at least a half-dozen garbage bags full of materials from Hatfill's apartment. But officials said no trace of anthrax was found in his home or at the storage unit.

The apartment complex is outside Fort Detrick, where Hatfill worked for two years for the Army Medical Research Institute of Infectious Diseases, center of the nation's biological warfare defense research.

Hatfill worked at the facility until September 1999. Although he probably had access to anthrax, his primary duties didn't involve working with it, a spokesman for the base has said.

Hatfill and another scientist, Joseph Soukup, commissioned a study of a hypothetical anthrax attack in February 1999 as employees of defense contractor Science Applications International Corp., said Ben Haddad, spokesman for the San Diego-based company.

The FBI has identified Hatfill as one of 20 to 30 scientists and researchers with the expertise and opportunity to conduct the anthrax attacks. The bureau has searched about 25 homes or apartments after getting permission from the people interviewed, a federal law enforcement official said.

Hatfill has not spoken publicly about the searches. In March, however, he denied involvement in the anthrax mailings and complained to The Baltimore Sun in a telephone message that he was fired from a recent job because of media inquiries.

``I've been in this field for a number of years, working until 3 o'clock in the morning, trying to counter this type of weapon of mass destruction, and, sir, my career is over at this time,'' Hatfill said.

Last month Hatfill was named associate director of Louisiana State University's National Center for Biomedical Research and Training, which is sponsored and financed by the Justice Department. Instructors travel around the country and train first responders, like emergency medical teams.

Hatfill, who previously was one of the adjunct instructors in the program, is moving to Baton Rouge, La., said Gene Sands, a university spokesman.

In New York City, meanwhile, a United Nations spokesman said Thursday that Hatfill attended a one-month training course in October 2000 to be a U.N. weapons inspector. The U.N. weapons inspection agency has been training people with expertise in chemical and biological weapons to work as inspectors if Iraq allows their return.

Hatfill is one of 230 people available for future weapons inspections, said Ewen Buchanan, spokesman for the U.N. Monitoring and Verification Commission, known as UNMOVIC. ``He is not on our payroll.''