MOSCOW - All but one of the 117 hostages who died amid an attempt to rescue them from a Moscow music hall were killed by the effects of an anesthetic gas used to knock out their captors, Russian health authorities said yesterday.
Dr. Andrei P. Seltsovski, head of the Moscow Department of Public Health, said only one of the hostages died of a gunshot wound. And only two of the 646 people who remain hospitalized were injured by gunfire. Forty-five were in critical condition.
The disclosure that the gas triggered the overwhelming majority of casualties followed public frustration over the failure of the Kremlin to explain what had happened during Saturday's pre-dawn raid.
And it came after bitter criticism by the hostages' families, scores of whom still did not know whether their loved ones were alive or dead almost 36 hours after the siege.
Moscow's top health officials, speaking at a news conference, pointed out that general anesthetics are safe when used in controlled conditions and with the proper dose, as in an operating room.
But the rescue force probably used a high concentration of anesthetic, health officials said, to make sure it knocked out the heavily armed Chechen guerrillas who had seized the 1,163-seat theater in an old community center, or Palace of Culture, in southeast Moscow on Wednesday night.
The guerrillas, who included 18 women, vowed to kill more than 750 hostages if the Kremlin refused to halt the war in Chechnya. They planted explosives throughout the building. The women strapped plastic explosives to their waists, wired to hand-held detonators.
Special anti-terrorist forces pumped the gas through the ventilating system minutes before troops shot their way into the theater about 5:30 a.m. Although none of the soldiers was seen wearing a gas mask, they began smashing windows as soon as they entered - apparently to disperse the gas.
All of the hostages who died, the physicians said, were weakened by almost 2 1/2 days of being forced to sit in theater seats and by the stress of their captivity.
"They didn't have food, they didn't have water," Seltsovski said. "Some of them had chronic diseases."
The youngest to die was a 14-year-old girl, who developed what doctors described as circulatory problems after inhaling the gas.
Of the 50 guerrillas inside the theater when the troops stormed in, all were killed. Many died, witnesses said, of a single gunshot to the head. Russian counterterrorism troops have been quoted as saying that they shot the groggy guerrillas to be certain that they did not trigger explosives.
The health department was not told about the use of the anesthetic gas until about the time of the raid, Seltsovski said.
Although he said he did not know exactly what drug was used, he said city hospitals had the necessary drugs and equipment to treat all of the more than 750 people who were in the theater.
The former chief of the anti-terrorism department of Russia's Federal Security Service, or FSB, called the use of the gas a "very radical sort of solution" to the standoff.
But Vladimir Lutsenko said yesterday that Russian and U.S. counterterrorism officials have talked in the past about using gas. And he said its use this time may have prevented the Chechen guerrillas from blowing up the theater and killing everyone inside.
"You saw that those terrorists had explosive devices on them," Lutsenko said in an interview. "And even the smallest error could have resulted in explosions."
If the Kremlin had negotiated with the Chechens, he said, it would have encouraged more hostage-taking. If the raid had ended with the Chechens killing most of the hostages, that would still have been seen as a coup for the terrorists.
So a rescue had to be carried out, even at the cost of some lives, Lutsenko said, or thousands more innocent people would have lost their lives in the future.
"I think that it was a full victory, a complete victory," he said, "not only for our country, but a victory for the whole community of those countries and people who fight terrorism."
Even some members of hostages' families hesitated yesterday to question the use of gas.
"I don't know of any other solution," said Tamara Mareva, 64, who was still looking for her son Igor, a 40-year-old violinist working in the theater. She and her family had spent almost 36 hours scouring Moscow's hospitals, without success.
"Of course, if everyone was alive, it is one thing," she said, hesitating. "But if it is your own son, nothing seems acceptable."
A few hours later, she was told that Igor was among those who had died. Authorities did not tell her the cause.
Seltsovski told reporters that autopsies will be conducted.
The Kremlin appears to be trying to keep tight control on information about the raid.
Last night's news conference marked the first time that officials had acknowledged that a gas was used. On Saturday, Deputy Interior Minister Vladimir Vasilyev would say only that "special means" were employed to subdue the guerrillas.
Officials have refused to say exactly what drug was used.
Russian President Vladimir V. Putin, in a televised address broadcast repeatedly over the weekend, apologized to families for not saving all of the hostages. But the Kremlin did not disclose what it certainly knew immediately - that the rescue operation itself was responsible for a significant number of deaths.
Relatives were barred for more than 24 hours from the hospitals where loved ones were taken. Only yesterday were the relatives allowed in - and then only to talk to doctors.
The first list identifying 51 of the dead was released late yesterday, more than 36 hours after the end of the siege.
Tatiana Karpova didn't know that her 30-year-old son, lyricist Alexander Karpov, had been killed until about 4:30 p.m. yesterday, when one of his friends called from a city morgue.
She was waiting at a center set up for the families of hostages, in the gymnasium of Vocational-Technical School No. 190, about a block from the theater. When she heard the news, she began to sob.
"People, what have you done?" she wailed, as her husband led her outside. "You sons of bitches! You sons of bitches!"
Like many of the hostages, Karpov was a successful young Muscovite. He had written a hit song, "A Long Road to Dublin," and he had translated the lyrics of the musical Chicago for its production here.
Earlier in the day, Tatiana Karpova bitterly recalled her treatment at the hands of government officials.
When hostages urged their families to protest against the war, Karpova helped try to organize a demonstration in Red Square. But the Kremlin would not permit a gathering there.
"Putin refused to permit a rally," she said. "For many of us, it was the last request of our children."
Then came Saturday morning, with its explosions, gunfire and ominous silence. After the troops stormed the theater, she recalled, an official happily declared that all of the hostages were safe.
"They said how we have won," she said. "We were all crying with happiness. Then it turned out to be a complete lie."
The Putin administration kept a tight rein on the news media during the hostage crisis, and there has been relatively little criticism of the Kremlin afterward on major television networks. Yesterday's broadcasts reminded older Russians of Soviet times of trouble - there was no news on most channels in the morning, only patriotic, Soviet-era films.
The lone independent voice during the hostage siege was news radio Echo Moskvy, which Muscovites came to rely on for unfiltered and uninterrupted news. The radio station was in the middle of a live interview at the moment the theater was raided. All of the television channels were showing entertainment programs.
Yesterday, a theater producer interviewed on Echo Moskvy talked sadly about the "problem of truth" in Russia - especially Russia's government.
Natalia Morosova, 62, of Moscow is not related to any of the former hostages, but like many Muscovites, she was transfixed by the crisis. She said she was very disappointed in the government.
"If the truth were told, it would be much better," she said. "We were told only half-truths. And half-truths are much worse than tragic, real information."
Many who were not allowed to see injured relatives in the hospital were angry.
"Why are the police trying to protect hostages from their relatives?" one woman demanded.
Some suspected that the government was trying to keep the former hostages from criticizing the raid.
"This is the FSB working," one man said.
There were numerous heart-breaking scenes yesterday. As one man sobbed against the wall at the Vocational Technical school gym, a group of anxious-looking psychological counselors came up. One urged him to take a tranquilizer.
"I don't need it," he said, pushing the counselor away.
At the entrance to Hospital No. 1, medical workers had posted a sign for the relatives of a hostage: "Woman, 14-20 years old ... yellow-metal earring in navel. Unidentified."
At one hospital, Sergei and Yelena Bochkov hunted in vain for their son Alyosha, a 25-year- old engineer. He had gone to the theater Wednesday, telling his parents he would be home late that evening. That was the last they saw of him.
"Our son is not on any list," she said. His mother pulled out family photos showing an athletic, cheerful young man on vacation by a lake.
"He is 1 meter, 86 centimeters tall," she said, "Handsome, too. We have many girls in our family, he's the only boy. He's a very good guy. Eight of his friends went to all the Moscow hospitals."
Tears began to stream down her face. She and her husband had reached their last hospital. They were on their way to register with authorities, who would try to match the pictures with bodies in the morgues.
"He's a very intelligent boy," she said.