A top Russian health official revealed Wednesday that the gas used in the raid on a Moscow theatre was based on fentanyl, an anaesthetic that does not ordinarily cause death.

Health Minister Yuri Shevchenko said fentanyl is not normally fatal but its effects were magnified because the hostages were dehydrated, hungry, and under severe psychological stress from being held captive for three days.

Fentanyl is a synthetic narcotic used for anaesthesia and analgesia. The biological effects of fentanyl is indistinguishable from that of heroin, with the exception that fentanyl may be hundreds of times more potent.

Earlier, Germany said samples from two German hostages showed traces of halothane, a gas used as an inhaled anesthetic.

"This material was detected in one of the two German hostages. It is possible a second unidentified material was also deployed," Munich coroner Ludwig von Meyer told a news conference.

Halothane was widely used in the mid-1980s but is hardly ever used now because is has lingering after-effects on the body.

The death toll of the deadly siege climbed Wednesday, as Russian officials announced the number of hostages who died had risen to 119. All but two died from complications caused by the gas used by Russian special forces to subdue the hostage-takers before they entered the theatre.

A Toronto resident among the lucky survivors was released from hospital Wednesday.

"Right now I'm very happy that I'm alive," Vesselin Nedkov told CTV Moscow corespondent Ellen Pinchuk. "For me it is my second birthday. It is my second chance."

On Tuesday, the U.S. ambassador to Russia said some of the hostages who died might still be alive if the Kremlin had been less secretive about the type of gas it used.

Alexander Vershbow told a news briefing that "the lack of information contributed to the confusion after the immediate operation to free the hostages was over."

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

Suspect ordered detained

Meanwhile, a court in Denmark has ordered senior Chechen official Akhmed Zakayev be remanded in custody pending an investigation into his alleged involvement in the theatre siege.

"The judge justified the detention by saying that there was risk that Zakayev would attempt to avoid prosecution if he were set free," Danish news agency Ritzau said.

Zakayev was arrested in Copenhagen earlier in the day at the request of Russian officials. He was in Denmark attending the World Chechen Congress.

Danish police said they received information from Moscow authorities on Tuesday which purportedly implicates Zakayev in the Moscow theatre siege. He's also suspected of taking part in other "terrorist" acts between 1996 to 1999.

"The Copenhagen police found this was sufficient foundation for the arrest," Danish police said in a statement.

Russian President Vladimir Putin angrily cancelled an official trip to Denmark scheduled for next month after learning that Zakayev had been permitted to travel there.

Danish Prime Minister Anders Fogh Rasmussen denied that his country's police had given in to political pressure from Moscow in making the arrest.

"This case has been treated according to normal police procedures," he told a news conference.

"I would find it very alarming if a government or an opposition interfered in the work of the police."

Zakayev is the most prominent spokesman of ousted Chechen President Aslan Maskhadov. Zakayev was deputy prime minister in Maskhadov's administration before the government was removed by Russian military in 1999.

Interfax news agency said an extradition request was being drafted.

"We are proceeding on the assumption that the Danish authorities will extend the necessary assistance to resolve this issue," Interfax quoted Deputy Russian Foreign Minister Valery Loshchinin as saying.

However, other Russian media reports said the Danish ambassador to Moscow ruled out extradition as Denmark has no extradition agreement with Russia.

Several dozen other people suspected of helping organize the attack have been arrested in Moscow, including a group of Chechens pulled over in a minibus. Police said the vehicle contained traces of TNT.

The lower house, the State Duma, has refused to form an independent commission to study how the hostage-takers had been able to successfully storm the theatre with large amounts of explosives and how police handed the crisis.