Russia's fatal use of an incapacitating gas to end a hostage crisis raises questions about whether the United States should continue looking for such means to calm large crowds or abandon the research altogether.
U.S. military and diplomatic officials said Monday the gas that killed more than 100 of the Moscow hostages was an opium derivative — part of a class of drugs that researchers suggested two years ago the Pentagon should investigate for development as nonlethal weapons.
Russian authorities have refused to identify the substance used, even to doctors treating the freed hostages. Hundreds remained hospitalized Monday, including more than four dozen in critical condition.
The United States and other countries have pressed Russia for information about the gas, but Russia has not responded, said State Department spokesman Richard Boucher. He said officials were trying to determine if one hostage killed was American.
U.S. officials believe the gas was an opiate, not a nerve agent. Opiates, a class of drugs including morphine and heroin, not only kill pain and dull the senses but also can cause coma and death by shutting down breathing and circulation.
Supporting the theory that an opiate was used was that Russian doctors treating the hostages told U.S. embassy workers they tried atropine — an antidote to many nerve agents — and that didn't work, a Bush administration official said. However, a drug that reverses the effects of opiates, Narcan, did appear to help, the official said.
Nevertheless, some medical experts questioned whether opiates were involved. Unless Russia has some secret chemical weapon, the only substance that could incapacitate people that quickly would be a form of nerve gas, said Dr. John Tinker, head of the anesthesiology department at the University of Nebraska Medical Center in Omaha.
The victims could have appeared to be unresponsive to atropine because the chemical is only a partial antidote and has no further effect after it reaches a certain level in the body, Tinker said.
"You could pump New York City's entire supply of gaseous anesthetics into that room and no one would go to sleep," Tinker said.
U.S. military research into so-called "calmative" agents is on hold amid worries such weapons would violate the international treaty banning chemical weapons.
However, the Justice Department has given $35,000 to Pennsylvania State University researchers investigating whether a calming drug could be added to pepper spray to make a better riot-control agent.
Russia also ratified the chemical weapons treaty, and officials for the pact's oversight body said Monday they may investigate the Russians' use of the gas.
The Marine Corps, which oversees nonlethal weapons programs for the Pentagon, asked the National Research Council to study existing and potential nonlethal weapons. That report, not yet released, supports developing incapacitating chemicals, said retired Army Col. John Alexander, a member of the research panel.
"We urged that, particularly with calmatives, they renew the research, and we don't think the legal argument against them is persuasive," said Alexander, who wrote a book on nonlethal weapons titled "Future War."
The international attention to the Russian case could put pressure on the United States to drop its research into calming or incapacitating substances, however.
"It's one of those very stark or definitive examples that nonlethal weapons are not a panacea. It's not the silver bullet that some people think it is," said Ron Madrid, a Penn State researcher who teaches a course on nonlethal weapons at the Marine Corps Command and Staff College. Madrid works for Penn State's Applied Research Laboratory, which is studying the calmative-pepper spray mix.
Madrid and other experts said the fact that the gas killed at least 116 hostages does not mean the hostage rescue operation was a failure. Fifty of the Chechen rebels holding the hostages also died in the early Saturday raid on the theater, including some who were shot in the head as they lay incapacitated by the gas.
"They had a situation in which they had people with large amounts of explosives that were likely to be used," Alexander said. "That's a situation that requires a very drastic response."
The Chechen rebels holding the hostages had wired themselves and the theater with explosives and threatened to kill all of the more than 800 hostages. If security forces had gone in with guns blazing, more hostages could have been killed, said Madrid, a retired Marine officer.
"It was somewhat successful in that not everyone died," he said.
Pentagon doctrine classifies nonlethal weapons as those meant to control the escalation of violence in a situation and minimize injuries and deaths. Lethal effects are still possible, however.
Russian officials have said the agent they used usually is not as deadly as it proved to be in the theater. The fact that the hostages had spent nearly three days under enormous stress with little food, water or sleep could have contributed to the high casualty rate, they said.
Indeed, one of the biggest problems with creating nonlethal weapons is determining what concentration to use. A dose enough to put an enraged, 220-pound soldier to sleep might be enough to kill a 10-year-old girl or an 80-year-old man. And a dose that incapacitates someone outdoors could kill when released inside a closed room.
"The difference between incapacitation and death is very small," Alexander said.