For nearly a decade, U.S. Army scientists at Dugway Proving Ground in Utah have made small quantities of weapons-grade anthrax that is virtually identical to the powdery spores used in the mail attacks that have killed five people, government sources say.

Until the anthrax attacks led to tighter security measures, anthrax grown at Dugway was regularly sent by Federal Express to the Army's biodefense center at Fort Detrick, in Frederick, where the bacteria were killed using gamma radiation before being returned to Dugway for experiments.

The anthrax was shipped in the form of a coarse paste, not in the far more dangerous finely milled form, according to one government official.

Most anthrax testing at Dugway, in a barren Utah desert 87 miles southwest of Salt Lake City, is done using the killed spores to reduce the chance of accidental exposure of workers there.

But some experiments require live anthrax, milled to the tiny particle size expected on a battlefield, to test both decontamination techniques and biological agent detection systems, the sources say.

Anthrax is also grown at the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, where it is used chiefly to test the effectiveness of vaccines in animals.

But that medical program uses a wet aerosol fog of anthrax rather than the dry powder used in the attacks and at Dugway, according to interviews and medical journal articles based on the research.

The wet anthrax, while still capable of killing people, is safer for laboratory workers to handle, scientists say.

Dugway's production of weapons-grade anthrax, which has never before been publicly revealed, is apparently the first by the U.S. government since President Richard M. Nixon ordered the U.S. offensive biowarfare program closed in 1969.

Scientists familiar with the anthrax program at Dugway described it to The Sun on the condition that they not be named.

The offensive program made hundreds of kilograms of anthrax for bombs designed to kill enemy troops over hundreds of square miles.

Dugway's Life Sciences Division makes the deadly spores in far, far smaller quantities, rarely accumulating more than 10 grams at a time, according to one Army official.

Scientists estimate that the letter sent to Senate Majority Leader Tom Daschle originally contained about 2 grams of anthrax, about one-sixteenth of an ounce, or the weight of a dime.

But its extraordinary concentration - in the range of 1 trillion spores per gram - meant that the letter could have contained 200 million times the average dose necessary to kill a person.

Dugway's weapons-grade anthrax has been milled to achieve a similar concentration, according to one person familiar with the program.

The concentration exceeds that of weapons anthrax produced by the old U.S. offensive program or the Soviet biowarfare program, according to Dr. Richard O. Spertzel, who worked at Detrick for 18 years and later served as a United Nations bioweapons inspector in Iraq

Lab security measures

No evidence linking the Dugway anthrax to the attacks has been made public, and there might well be none. Army officials say the anthrax there and at Fort Detrick has long been protected by multiple security measures.

The FBI has extensively questioned Dugway employees who have had access to anthrax, according to people familiar with the investigation.

Agents also have questioned people at Fort Detrick and other government and university laboratories that have used the Ames strain of anthrax found in the letters.

Still, the analysis of the genetic and physical properties of the anthrax mailed to Daschle and Sen. Patrick J. Leahy has caused investigators to take a hard look at Dugway's anthrax program.

First, the genetic fingerprint of the mailed anthrax is indistinguishable from that of the Ames "reference strain," which is the strain used most often at Fort Detrick and Dugway, according to a scientist familiar with the genetic work.

Researchers led by Paul Keim at Northern Arizona University have compared the two samples and found them identical at 50 genetic markers - the most sensitive genetic identification method available.

That does not mean the mailed anthrax necessarily originated from an Army program, because Ames anthrax has been widely used at government and university laboratories in the United States and overseas

Shipped without records

While some sources have estimated Ames might have been used in as few as 20 labs, one scientist who has worked with anthrax said the total cannot be known exactly, but is probably closer to 50.

"Until the last few years, a graduate student would call up a friend at another lab and say, 'Send me Ames,' and they'd do it," the scientist said. "There wouldn't necessarily be any records kept."

Ames is similar to but distinct from the Vollum1B strain of anthrax used in the old U.S. offensive biological weapons program.

The genetic testing proves the mailed anthrax was not left over from the old program, most scientists agree.

Even more provocative than the genetics are the physical properties of the mailed anthrax. While some scientists disagree, many bioterrorism experts argue that the quality of the mailed anthrax is such that it could have been produced only in a weapons program or using information from such a program.

Link to Dugway base

If true, that would greatly limit the field, increasing the likelihood of a link to the only site in the United States where weapons-grade anthrax has been made in recent years.

Dugway, which is larger than Rhode Island, has been a military testing ground since World War II, when military officials selected it for its remote location in Utah's Great Salt Lake Desert.

The Dugway anthrax program was launched in the early 1990s, shortly after the Persian Gulf war reawakened U.S. military commanders to the threat from biological weapons.

Iraq is known to have built a major bioweapons program that included anthrax in its potential arsenal.

According to Dugway's Web site, the proving ground's Life Sciences Division has an aerosol technology branch and a biotechnology branch, both of which use a Biosafety Level 3 laboratory designed to contain pathogens.

Anthrax and other dangerous germs at Dugway are guarded by video cameras, intrusion alarms, double locks and a buddy system that does not permit workers to handle the agents alone, according to one scientist.

But Dugway does not have a gamma radiation machine, which is why its anthrax has been shipped to Detrick for irradiation.

Dr. David L. Huxsoll, who headed Detrick's biodefense program in the 1980s, said vaccines and detection systems must be tested against aerosolized anthrax if troops are to be prepared for biological attacks.

"When you're building a program to defend against biological weapons on the battlefield, you have to be prepared for an aerosol exposure," he said.

Not a treaty violation

Milton Leitenberg, an expert on bioweapons at the University of Maryland, said he was not aware of the Dugway anthrax production.

But he said making a few grams of weapons-grade anthrax for testing defensive equipment would not violate the international convention on biological weapons.

The treaty bans the production of bioagents "of types and in quantities that have no justification for prophylactic, protective and other peaceful purposes."

"There's no specific limit in grams or micrograms," Leitenberg said. "But if you got up in the hundreds of grams, people would be very, very skeptical."

The FBI's investigation, called Amerithrax, has focused on the possibility that the anthrax terrorist might be a loner in this country with some scientific training.

The Sun reported Sunday that in two months, none of the hundreds of FBI agents on the case had contacted the Army retirees who produced anthrax in the 1950s and 1960s.

Yesterday, one of those anthrax veterans, Orley R. Bourland Jr. of Walkersville, got a call from the White House Office of Homeland Security seeking information.

The FBI had not made contact with several veterans interviewed yesterday.