DENVER (AP) -- A Japanese cult attacked Tokyo in 1993 with an innocuous, readily available strain of anthrax sold by a Colorado animal vaccine company, an Arizona researcher said.

The anthrax was used by the Aum Shinri Kyo doomsday cult that in 1995 used sarin nerve gas to kill 12 people in an attack on a Tokyo subway station.

Paul Keim, an anthrax expert at Northern Arizona University in Flagstaff, told colleagues about the 1993 anthrax attack at Sunday's session of the American Association for the Advancement of Science convention in Denver.

Using DNA, researchers at the university traced the microbe to the Sterne strain produced by Denver-based Colorado Serum Co. The company makes a vaccine used by farmers worldwide to prevent anthrax in livestock.

The Sterne strain lacks a fragment of DNA necessary for the bacteria to cause disease.

"The cult was using a vaccine strain, which wasn't virulent," Keim said.

Colorado Serum officials did not return an after-hours phone call on Monday.

The same technique of genetic fingerprinting was used to unravel the source of the anthrax that killed five in the United States in 2001. Keim said he could not talk about the U.S. attack because he has a nondisclosure agreement with the FBI.

In 1993, Japanese public health authorities had been tipped off about an eight-story building the Aum Shinri Kyo cult owned in Kameido, a suburb of Tokyo. Neighbors lodged 160 complaints about a terrible stench coming from the building, Keim said.

Public health investigators took photos of smoke rising from the building's roof and scraped slime samples from its walls.

Their concern was that the cult and its leader Shoko Asahara were boiling the bodies of assassinated victims.

It turned out the cult was growing anthrax in the basement in a vat and was pumping it from the building's roof. The cult was also using a white utility van with special vents to spew anthrax-tinged gas through neighborhood streets.

"If authorities at the time had recognized this as a bioterrorist attack, perhaps the sarin gas attack would have never occurred," Keim said.

Instead, the anthrax plot wasn't discovered until cult members released nerve gas in one of Tokyo's most congested subway stations during rush hour in 1995. After their arrests for that incident, cult members mentioned the earlier anthrax attacks.

Four of five vials containing the slime had been analyzed by Japanese scientists looking for proteins that would have confirmed rumors the cult processed human remains at the building. One dusty vial remained in a public health refrigerator.

Keim cultured the sample in a petri dish filled with sheep blood. The sample blossomed with the telltale shape of anthrax blooms. Of the 4,000 activated spores that crowded the petri dish, the lab ran DNA fingerprints for 48, matching them to the Sterne strain.

While some said the cult was incompetent, Keim believes its leader Asahara had such a hold on his followers, who included graduate level microbiologists, that some may have been afraid to tell him they did not have deadly material.

Hiroshi Takahashi of Japan's National Institute of Infectious Diseases has said no one reported symptoms after the attack, which lasted 24 hours.

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