Stored slime reveals why release went undetected. (Cult Anthrax).

A sample of mysterious ooze has shed new light on the use of biological weapons in 1993 by the Japanese cult Aum Shinrikyo.

The cult achieved worldwide notoriety in March 1995 for releasing sarin, a deadly nerve gas, in the Tokyo subway system. It killed 12 people and sickened some 5,000 more. Evidence now shows that 2 years before that, the cult released anthrax in Tokyo, says Paul Keim of the Northern Arizona University in Flagstaff. At the time, however, nobody noticed anything more serious than an annoying smell.

This week in Denver at the annual meeting of the American Association for the Advancement of Science, Keim and his colleagues expanded on the drama behind their previously published technical account of how the anthrax release proved to be a life-sparing dud.

The cult owned an eight-story building in the section of the Tokyo metropolitan area called Kameido. During 4 days in mid-1993, public health officials logged some 160 complaints about how bad the place smelled. The officials never gained access to the building, Keim said, but the government did take photographs of a structure on the roof that was puffing out a white mist. Workers also collected samples of what Keim describes as "slime" dripping down the side of the building.

Because officials suspected the cult might have been cooking bodies down for disposal, they had the slime analyzed for human proteins, Keim said. None was found.

The investigation stalled for 2 years. After the subway attack with sarin gas, Japanese officials questioning cult members turned up mentions of earlier anthrax releases. Epidemiologist Hiroshi Takahashi of Japan's National Institute of Infectious Diseases in Tokyo learned that one sample of wall slime obtained during the 1993 investigation remained in storage, and he shipped it to Keim's genetics laboratory.

The slime indeed held the bacterium Bacillus anthracis, the researchers reported in Deccember 2001. They also explained why no one had died. Keim and his colleagues determined that the cult had released a harmless anthrax strain called Sterne, which is used in both the United States and Japan for making anthrax vaccines.

Trained microbiologists worked for the cult, so Keim says he doubts that they used a harmless strain out of incompetence. Instead, they might have been testing their setup with a harmless surrogate. Or, says Keim, the people who set up the rooftop release might have been too afraid of the violent leader to admit that they couldn't procure a killer strain of anthrax.

FBI biocrime specialist Bruce Budowle speculates that if authorities had managed to detect this early anthrax release, "perhaps the sarin gas attack would never have happened." To buttress U.S. capacity for coping with biocrimes, Budowle, Keim, and a committee of other specialists released a report in Denver calling for improved cooperation between the public health and law enforcement communities.