On 26 October 2002 after a two-and-a-half day siege at Moscow's Dubrovka Theatre. where the popular musical Nord-Ost was showing, FSB and police special forces pumped an undisclosed chemical agent into the theatre's ventilation system at the beginning of an operation to release the 912 hostages held by 40 armed Chechen militants led by Movsar Barayev demanding the withdrawal of Russian forces from Chechnya and an end to the Second Chechen War. All 40 terrorists were reported killed, with no casualties among the special forces. Some 130 hostages died as a result of adverse reactions to the gas. Two of the hostages were killed by the militants. The authorities refused to disclose the identity of the gas.