§ Alan Simpson
To ask the Secretary of State for Foreign and Commonwealth Affairs what assurances he has(a) sought and (b) received that the gas used by the Russian authorities was not in violation of the 1993 Chemical Weapons Convention. 
§ Mr. Mike O'Brien
Following inquiries by the United Kingdom and others, Russian authorities have announced that the gas used in ending the siege on a Moscow theatre, on Saturday 26 October, was based on Fentanyl, an opium based narcotic. Fentanyl is not a chemical scheduled under the Chemical Weapons Convention. Non-scheduled chemicals are not in themselves prohibited under the Convention for use in law enforcement, including domestic riot control purposes. On 30 October, the Russian Health Minister, Mr. Shevchenko said "I officially declare that chemical substances of the kind banned under international conventions on chemical weapons were not used".