WASHINGTON -- Five years after a series of deadly anthrax-laced letters rattled the nation, the FBI has offered no indication that it is any closer to solving the first major act of bioterrorism on U.S. soil, leading critics to speculate that the probe has stalled and to question how well federal officials would handle future attacks.
Members of Congress and targets of the attacks - which killed five people between Oct. 5 and Nov. 21, 2001, sickened 17 and exposed thousands of others - are increasingly expressing dismay that the FBI-led federal investigation, code-named Amerithrax, has been mismanaged.
FBI officials have stopped providing regular briefings to victims and lawmakers about the investigation. The federal task force leading the investigation has shrunk in half. And it is now on its third leader.
The credentials of the latest chief may be telling: He has worked on complex international criminal cases that have run cold.
The reticence of the FBI is in sharp contrast to bold predictions the agency made about the investigation in its early days.
"Their public pronouncements about their confidence levels were obviously way off the mark all the way along," said Tom Daschle, the former Democratic senator from South Dakota whose Capitol Hill office was one of the targets of the attacks. "It has sort of been the domestic version of Iraq. They made a lot of assumptions that turned out not to be accurate."
Daschle, now a senior fellow at the Center for American Progress, said he asked the FBI about a month ago for an update but was rebuffed.
"Clearly, this whole investigation has gone very cold," he said. "Because it has become so cold, they are all the more apprehensive about acknowledging that they do not have any real good evidence or leads."
A leading Republican, Sen. Charles E. Grassley of Iowa, also complained about the lack of new information on the investigation in a letter last month to Attorney General Alberto R. Gonzales. Grassley is threatening to subpoena FBI officials to testify before Congress or to hold up Justice Department nominations if the agency does not divulge more information soon.
The FBI says its investigation remains highly active. It has told lawmakers that it would not provide any more briefings on the case in part out of fear that sensitive information would be leaked to the media.
"We have a substantial number of agents continuing to work on that case, and my expectation is that it will be solved and that the person or persons responsible will be brought to justice," FBI Director Robert S. Mueller III said in an interview in September. "Some cases take longer than others."
The unsolved mystery comes amid growing concern about federal efforts to detect and prevent even more catastrophic bioterrorist attacks. The government has set aside an estimated $18 billion for bio-defense research over the last five years, although it is far from clear what the nation has gotten for its money.
Earlier this week, recognizing the five-year anniversary of the anthrax attacks, a bipartisan group of senators asked the Government Accountability Office to conduct a wide-ranging assessment of the bio-defense program.
The anthrax attacks triggered one of the federal government's costliest manhunts ever - starting just a week after the Sept. 11 attacks - when letters containing anthrax began coursing through the mail, targeting members of the news media and the Capitol Hill offices of Daschle and Sen. Patrick J. Leahy, a Vermont Democrat.
The FBI said it has conducted 9,100 interviews and obtained 6,000 subpoenas. It has hired psychologists, handwriting analysts and forensic analysts. It has spent millions on scientific studies to determine everything from the strain of the bacteria to the water used to prepare the lethal spores. And it has tracked a spate of anthrax "hoax" letters; one such letter was received late last month by the Los Angeles Times.
Much of the initial public focus was on a medical doctor and virologist, Stephen J. Hatfill, who had worked for two years at an Army lab in Maryland, where the strain of anthrax used in the attacks was once studied.
FBI agents searched his home, took his blood and put him on a 24-hour surveillance. Then-Attorney General John Ashcroft declared him a "person of interest."
But Hatfill was never charged and says he is not responsible for the letters. Now, he's fighting the Justice Department and FBI in a lawsuit claiming that they destroyed his reputation.
His lawyers have taken the sworn testimony of more than 30 journalists and investigators in an attempt to prove that the FBI illegally leaked damaging information about him. Hatfill declined comment through his lawyer.
The public naming of Hatfill was the first of many missteps that experts said have afflicted the probe.
In the recent interview, Mueller said, "From the outset, we have been open to any and all theories, and the investigation continues on any and all theories."
But some observers said that the incorrect assumptions about the anthrax may have led the FBI to adopt an unduly narrow focus on potential suspects. According to one former federal law enforcement official, no other clear suspects have emerged in the case in recent years.
Some also have criticized the agency for not being more receptive to outside advice. Dr. Ken Alibek, a bio-weapons pioneer from the former Soviet Union, said he wrote to Mueller to volunteer. "I said please keep in mind, I have expertise and I would like to help you resolve this case," he said. Alibek said he got a "thanks, but no thanks" letter from a top aide to Mueller. The bureau, he was told, already had "a big group of people working on this issue."
Richard B. Schmitt and Josh Meyer write for the Los Angeles Times.