Photo by Doug Koontz William Henry Main Jr., who lives on Military Road, has been a neighbor of Fort Detrick since 1953. His house overlooks Detrick near the old PX.

FBI spokeswoman Debbie Weierman said 18 FBI special agents and 10 U.S. postal inspectors are still working full-time on the case, dubbed “Amerithrax,” but declined to provide additional details about the status of the investigation.

In October 2001, the FBI turned to USAMRIID to test thousands of items and environmental samples for anthrax. A USAMRIID team worked around the clock, in three shifts of eight hours, until May 2002.

During the FBI’s investigation, USAMRIID, the Army’s lead biodefense laboratory, came under scrutiny. The Ames anthrax strain used in the attacks originated at USAMRIID, though Ames was distributed to a small number of biodefense labs.

The advanced technology used to produce the refined form of anthrax used in the letters appeared to be the work of an expert — the FBI suspected the mailer could be one of USAMRIID’s own scientists.

In June 2002, the FBI named former USAMRIID biowarfare researcher Dr. Steven J. Hatfill “a person of interest.”

FBI agents searched Dr. Hatfill’s apartment across the street from Fort Detrick and searched a locker he rented in Ocala, Fla.

In December 2002 and January 2003, agents searched a frozen pond in the Frederick watershed for evidence used in the 2001 attacks and found a clear box with holes that could accommodate gloves, a device that may have been used to prepare the envelopes.

The FBI drained the pond in June 2003, looking for equipment and clothing the mailer used to work with anthrax. After three weeks of work, they found nothing.

In August 2003, Dr. Hatfill sued the FBI and the Justice Department saying they had wrongly targeted him as the person who mailed the anthrax letters and violated his civil rights and privacy.

In July 2004, he sued The New York Times and columnist Nicholas Kristof in federal court in Alexandria, Va., for implying he was guilty of the crimes, claiming defamation and intentional infliction of emotional distress.

A federal judge threw out Dr. Hatfill's lawsuit against The Times, but the 4th U.S. Circuit Court of Appeals reinstated the suit. The Supreme Court declined to take up the case.

On March 27, the Supreme Court refused to block Dr. Hatfill’s defamation lawsuit against the newspaper.

Following the 2001 anthrax attacks, current and former USAMRIID scientists reported a lax security system at the institute that would have been ineffective against an employee smuggling out anthrax or other biological terrorism agents.

Dr. Frank Malinoski, a former USAMRIID medical virologist, said USAMRIID’s safety and security measures are largely effective against inadvertent breaches in containment, but deliberately smuggling out an agent such as anthrax is “theoretically possible.”

Safeguards against individuals intentionally smuggling out agents include security clearances and checking credentials, Dr. Malinoski said.

“It comes down to intent — someone has to do that on purpose,” he said.

In December 2001, The Hartford Courant in Connecticut reported its interviews with more than a dozen USAMRIID scientists who detailed security problems, including a lack of accountability for deadly agents and scientists working alone in labs at night.

Former Army scientist Richard Crosland, who worked at USAMRIID until 1997, told The Washington Post that convenience stores kept better records than USAMRIID.

USAMRIID officials said since the institute’s inception in 1969, laboratory personnel have been required to track agent use through a paper system, and now scientists track agents in an electronic system.

Each agent is registered down to the individual researcher using the agent, allowing USAMRIID to monitor unapproved agent use, Safety Officer Maj. Chris Ansell said.

USAMRIID uses an institute-wide agent registry as well as a select agent registry. Select agents are identified by the Centers for Disease Control and Prevention as those that have the potential to threaten public health and safety.

Select agent regulations mandate that all labs possessing these agents, not just those shipping and receiving them, register with the CDC. USAMRIID works with select agents such as Bacillus anthracis (the causative agent of anthrax), Botulinum neurotoxins, ebola viruses and marburg virus.

USAMRIID spokeswoman Caree Vander Linden said researchers must notify their supervisors and Institute security if they’ll be working after-hours and provide information on what times the researcher will be in the building and what he or she will be doing.