FBI agents searching a pond near Frederick for clues in the 2001 anthrax attacks finished their work and left the area yesterday after finding no additional physical evidence to immediately suggest any links to the case, law enforcement sources said.

Those sources said the FBI took soil samples from the bottom of the pond for testing. Investigators earlier this month diverted 1.45 million gallons of water from the pond and began sifting through mud for clues to the case that brought the prospect of bioterrorism into the average U.S. household.

Frederick Mayor Jennifer P. Dougherty said the FBI told her yesterday that "they found a bicycle, some logs and a street sign," leaving the items for workers to dispose of in a public landfill. She said it was unclear whether that was a complete list of what was found. Law enforcement officials said other items found in the pond included coins, fishing lures and a handgun, which was given to local authorities.

The FBI began draining the one-acre pond in the Frederick Municipal Forest, about eight miles from downtown Frederick, on June 9. Investigators were hoping to find clues that could lead to an arrest in the attacks, which killed five people and sickened 17 others who were infected by anthrax bacteria sent through the mail.

The pond is about eight miles from the Army Medical Research Institute of Infectious Diseases at Fort Detrick in Frederick, one of the nation's primary anthrax research centers. It is one of several ponds searched by divers in December and January after FBI officials had received a tip that a bioterrorism expert who formerly worked as a researcher at the institute once talked hypothetically about how he might dispose of contaminated materials in water. That researcher, Steven J. Hatfill, has been described by Attorney General John D. Ashcroft as a "person of interest" in the investigation. His apartment was next to Fort Detrick.

Hatfill has denied any involvement in the attacks.

In May, law enforcement sources said FBI investigators found laboratory equipment of interest to them in those earlier searches. Yesterday, all that remained at the pond was a plastic mesh fence the FBI erected around its perimeter.

The fence was "for safety reasons," Dougherty said, to keep people away from the spring-fed pond while it refills, a process that will take seven to 10 days.

Dougherty said the FBI told her yesterday that "they are done" at the pond. "They are leaving. I don't have any expectation that they'll be back in this area, in the watershed." However, she said, "They've given us no indication that they're out of Frederick County."

The latest operation in the forest was expected to end within a month and cost about $250,000.

Staff writer Allan Lengel contributed to this report.

This month, investigators diverted 1.45 million gallons of water from the pond to search for anthrax terrorism apparatus.