By Judith Ingram, Associated Press, 10/30/02

MOSCOW -- Russia's top health official said Wednesday that the gas used in the storming of a Moscow theater held by Chechen gunmen was based on fentanyl, a fast-acting opiate with medical applications, Russian news agencies reported.

Health Minister Yuri Shevchenko said the compound was an anesthetic and would not normally cause death, the Interfax and ITAR-Tass news agencies reported.

"By themselves, these compounds cannot provoke a fatal outcome," Shevchenko was quoted as saying.

The announcement appeared to be an attempt to counter criticism, especially from foreign governments, that Russian officials were being too secretive and that the lack of information about the gas used in the special forces raid on Saturday may have increased the number of fatalities. At least 117 of the hostage-takers' victims were felled by the gas.

But Shevchenko said that the deaths were caused by the use of the chemical compound on people who had been starved of oxygen, were dehydrated, hungry, unable to move adequately and under severe psychological stress.

"It is precisely these factors that led to a fatal outcome for some of the hostages," Shevchenko said.

The incapacitating gas was intended to prevent the hostage-takers from triggering explosives strapped to their waists and rigged around the theater. It worked but it also knocked out most of the hostages.

On Tuesday, the U.S. ambassador to Moscow, Alexander Vershbow, said the lack of information provided by Russian authorities "contributed to the confusion after the immediate operation to rescue the hostages was over."

"It's clear that perhaps with a little more information at least a few more of the hostages may have survived," he said.

Dr. Thomas Zilker, a toxicology professor at Munich University Clinic in Germany, said Wednesday that blood and urine samples from two Germans among the former hostages showed traces of halothane, a gas used as an inhaled anesthetic. He said he believed the gas pumped into the theater likely also contained other substances.

The hostage-takers seized the theater, with more than 800 people inside, on Oct. 23. They demanded that Russian President Vladimir Putin withdraw Russian troops from Chechnya, where the most recent war began in 1999.