More than two weeks after anthrax bacteria turned up in the American workplace, the evidence that has come to light has only heightened the mystery of who is behind the scares: domestic radicals, foreign terrorists, another nation or a lone, disaffected American.
The latest information, including technical details of the bacteria involved, has only intensified the debate over who mailed anthrax letters to media outlets and a congressional office. The anthrax bacteria appear to have been prepared in a way that shows some sophistication, but not so much that it probably came from a top-grade foreign weapons program, several experts said.
"The information doesn't tell you much," said Eric Croddy, a biological weapons expert at California's Monterey Institute of International Studies. "It leaves a lot of people who could have done this."
An FBI investigator who spoke on condition of anonymity agreed, saying: "That's the big question right now: Who's doing this? Some disgruntled wacko taking advantage of the current paranoia, or did it come from Afghanistan or Russia or Iraq? Nobody knows."
For a nation still setting the boundaries of its war on terrorism, the question of who is behind the anthrax attacks has huge ramifications.
The U.S. already has declared the Al Qaeda terrorist network an enemy, and it is doing what it can to destroy the group. Evidence that a domestic group or Unabomber-style individual mailed the bacteria would lead to the kind of criminal investigation already familiar to Americans.
But if a foreign nation such as Iraq played a role, it could open a whole new front in the war.
Moreover, without knowing the origin of the bacteria, federal officials are unable to say whether the bioterrorism will continue.
"I wish I could tell you that we've seen the end of it, but we obviously are preparing for more," Tom Ridge, President Bush's director of homeland security, said Friday.
A range of circumstantial evidence points to each of the potential suspects.
U.S. officials say there are ample indications that Osama bin Laden has sought biological and chemical weapons. It is unclear whether he succeeded. But officials were disconcerted to learn last month that Mohamed Atta, one of the suspected Sept. 11 hijackers, had shown interest in Florida crop-dusting airplanes, which might be used to spread biological or chemical weapons.
Law enforcement officials said Friday that they had traced at least one anthrax-tainted letter, the one to NBC news anchor Tom Brokaw, to a single mailbox in Ewing, N.J. The anthrax-tainted letter to Senate Majority Leader Tom Daschle (D-S.D.) was postmarked in Trenton, N.J. Several hijackers in the Sept. 11 attacks had lived in New Jersey.
Circumstantial evidence also suggests a possible role for Iraq. Even before the anthrax attacks, investigators probing the Sept. 11 hijackings wanted to find out more about a meeting this year in Europe between Atta and an Iraqi intelligence agent.
Iraq's interest in biological weapons dates back more than a decade. In the mid-1990s, Iraqi officials admitted to having a large bioweapons program, but they said they destroyed their anthrax stocks in 1991.
But after the Persian Gulf War, U.N. inspectors discovered that Iraq had imported specialized spraying equipment, industrial dryers and bacterial growth nutrients that could be used in a continuing effort to make biological weapons.
"If you ask if Iraq is capable of producing this material, the answer is an unequivocal yes," said Richard Spertzel, a microbiologist who led the U.N. biological inspections team in Iraq. "If you ask whether they did it, I don't know."
Several administration and law enforcement officials downplayed the notion that Iraq helped with the anthrax scares.
"I have not seen anything that tells me there is a link between the anthrax and Iraq," one Bush administration official said Friday. "We don't know for sure, the FBI hasn't reached final conclusions, but we haven't seen a link."
Another Bush administration official agreed, saying he too had seen "no linkage."
A law enforcement official, speaking about Iraq's possible involvement, said: "The only people I hear speculating are the media. It's a subject that just has not come up."
Officials also say they cannot dismiss the idea that a domestic group is behind the scares.
The writing on the anthrax-tainted letters "is the writing of a native-born English speaker, not someone who's been in the country a few years," said Vincent Cannistraro, former chief of counter-terrorism at the CIA. He added that the letters were addressed to media and government targets that some people see as liberal icons.
Several leaders in the anti-government movement said they believe it is possible that the anthrax scares came from a U.S. citizen who believes authorities will not find him in their search for suspects abroad.
"You've got one person somewhere who's doing this. I don't think it's a terrorist plot any more than the Unabomber was a terrorist plot," said Clay Douglas, who runs the Free American magazine and radio network out of his home in rural New Mexico.
Bo Gritz, a former Vietnam War commando, believes the envelopes may be coming from some isolationist, religious compound.
"You've got people who gang together . . . who hope for an Armageddon because their own lives are so miserable," he said in a phone interview from his home in Sandy, Nev. "They have been praying for something to happen, and the attacks on the World Trade Center give them an excuse to make it happen."
In recent years, Americans have been found with dangerous biological agents on several occasions.
Larry Wayne Harris, an Ohio white supremacist, pleaded guilty to wire fraud for obtaining a mail-order shipment of the germ that causes bubonic plague in 1995. In 1998, he was charged with possessing anthrax, and boasted that he had enough to "wipe out" a city. _ _ _ Times staff writers Eric Lichtblau, Josh Meyer and Greg Miller contributed to this report.