By JOSEPH B. VERRENGIA AP Science Writer

October 26, 2002, 6:12 PM EDT

Military experts and toxicologists say Russian commandos probably pumped a gas containing Valium into a Moscow theater to subtly disable and disorient heavily armed Chechen rebels prior to Saturday's dramatic assault.

Russian authorities didn't identify the gas used in the operation, which freed hundreds of hostages but also resulted in the deaths of more than 100 captives and rebels. Officials claimed none of the hostages were killed by the gas.

Several nations, including the United States, have developed a variety of non-lethal incapacitating agents, which can also induce choking, nausea or blurry vision, depending on their recipes.

According to some hostages inside the theater, they realized they were becoming sleepy and confused, but no one reported seeing a vapor cloud, smelling a chemical or experiencing the sort of irritating symptoms associated with tear gas and pepper spray.

Experts said the Russians may have released a gas concentration of a powerful sedative like Valium or may have used a form of BZ gas, a hallucinogenic drug widely researched in the 1960s that works more slowly.

"The thing that pops into my mind is aerosolized Valium," said Dr. Christopher Holstege, medical toxicology director at the University of Virginia. "But there isn't much literature out there on it. There is talk of using it as a riot control agent."

Others said the agent used by the Russians didn't seem to be like anything that has been part of the U.S. arsenal.

"It's no surprise that the Russians have that kind of stuff," said Ron Madrid, a former Marine and an expert on non-lethal weaponry at Pennsylvania State University. "They spent 30 years putting it together. We're prevented from doing that by treaty and executive order."

Russian television reported the gas was dispersed through the theater's ventilation system. Workers were seen digging around sewers and steam pipes near the theater in the first day of the crisis.

One Interfax News Agency employee among the captives in the theater said the rebels appeared ready to kill all the hostages, "then something happened."

"I lost consciousness and woke up in the emergency room," said Olga Chernyak. "It must have been some special gas."

Outside City Hospital No. 13, Galina Dolotova said her 32-year-old daughter, Olga, appeared to have been one of the hostages least affected by the gas, but even at that "she was in terrible shape" when she was brought in.

Holstege said people exposed to aerosolized Valium would feel sleepy and confused. At sufficiently high levels, it could compromise breathing and oxygen supply to vital organs.

"It sedates you, so you would feel hung over," Holstege said "People don't remember events well afterward. If it was administered in a theater full of people with guns and explosives, it might confuse them as to what was going on so they could not shoot."

Experts also mentioned BZ, or 3-quinuclidinyl benzilate, as a possibility for the gas used by the Russians.

BZ was a research focus of the U.S. Army during the Cold War at the former Edgewood Area labs near Washington. It belongs to a class of drugs known as anticholinergics that interrupt the brain's chemical messaging system between cells, leading to confusion and hallucinations. It needs an hour to take effect, so authorities would've had to release it into the theater long before the actual assault.

BZ also produces a tendency to fall asleep, and government reports show that soldiers in its U.S. development program nicknamed it the "sleeping agent." The delirium it induces can last two or three days.

"The Russians could've used BZ in the theater, but perhaps in higher concentrations," Holstege said.

A recent U.S. Air Force paper on nonlethal weapons said "calmative" agents reportedly were used by Soviet troops against Afghan guerrillas during their 1980-89 war.

The American and British militaries have discussed developing calmative weapons that would incapacitate or repel people. The effort intensified in the 1990s after hostile mobs confronted U.S. troops during peacekeeping and humanitarian missions in places like Somalia, Bosnia and Haiti.

In 2000, researchers at a Pentagon-funded institute at Penn State prepared a 50-page report that said developing calmative weapons "is achievable and desirable" and suggested drugs like Valium for further research.

However, it is unclear whether such weapons would violate the convention banning the use of chemical weapons, officials said.

-- Anonymous, October 26, 2002