Russia has identified the gas used to end the weekend theatre siege in Moscow with the deaths of 119 hostages.
The Health Minister said the gas was an opiate based on Fentanyl - a potent narcotic used as an anaesthetic.
There are reports of growing anger in Moscow at the government's refusal to name the gas, hindering the treatment of survivors, many of who remain in a critical condition.
Earlier, a court in Denmark ordered the detention for two weeks of a prominent Chechen exile in response to a Russian request for extradition.
Russia alleges that Akhmed Zakayev helped to plot last week's siege.
