With almost daily reports of anthrax scares, government officials say they cannot rule out the possibility that the threats may be the work of homegrown terrorists.
"We would be doing ourselves and the country a disservice to not be looking over our shoulder and keeping track of what the domestic right-wing hate groups are doing and saying," said Daniel Levitas, a hate-group analyst based in Georgia.
Sources tell ABCNEWS it is unlikely that domestic extremists could produce the kind of sophisticated anthrax that was mailed to the U.S. Capitol, because of the money, the expertise and the precise equipment that is required. But domestic extremists cannot be completely dismissed.
They have proved their capacity for terrorism, from the Oklahoma City bombing to the 1984 case in which Rajneeshi militants caused a salmonella outbreak that sickened more than 100 Oregon residents.
Literature produced by domestic militants often contains recipes for terror, and some extremists in the United States have tried to obtain biological or chemical agents. The best known is Larry Wayne Harris, a self-described former neo-Nazi who was arrested twice for possessing bubonic plague and a third time for holding an inactive form of anthrax.
In 1998, Harris told ABCNEWS' Diane Sawyer that biological weapons were attainable. "I'll tell you one thing that I know almost beyond any shadow of a doubt is that there [are] groups in the United States with biologicals. But they're armed with a very crude biological. It's effective," said Harris.
Taking Advantage of Crisis
So far, such threats have rarely gone beyond just talk. Nonetheless, militants in this country are poised to take advantage of the current climate of fear and panic.
"They look at the fear and panic created in places like New York an they actually are encouraged by that because they want to see more confusion in society. In their deranged outlook on the world, it presents to them not a crisis but an opportunity," said Levitas.
Of the more than 100 anthrax hoaxes at abortion clinics, authorities say many have been linked to the Army of God, a militant anti-abortion group.
"You know these days if you sent white powder to an abortion clinic you can be pretty well assured that the clinic will be shut down," said Mark Potok, who monitors hate groups for the Southern Poverty Law Center and edits the group's magazine, Intelligence Report.
Goal: Spread Panic
For extremists, the hoaxes are a weapon in themselves, says Jessica Stern, a terrorism expert at Harvard University. The goal, she says, is to spread the panic and stretch the resources of law enforcement.
"Hoaxes are an incredible act of terrorism," said Stern.
"They understand that the FBI has a limited amount of manpower," said Stephen Gale, who teaches classes on terrorism at the University of Pennsylvania. "We don't have any surplus manpower. We have only so many trained investigators, we have so many trained cops to do this kind of work."
Which presents another worry: That law enforcement will be too busy to keep track of militants in the United States who in the past have turned their homegrown hatred into destruction.