German medical experts said today Russia probably used an anaesthetic called halothane to knock out Chechen rebels holding hundreds captive in a Moscow theatre.
"It is probably an anaesthetic called halothane," said Munich coroner Mr Ludwig von Meyer at a media conference.
"This material was detected in one of the two German hostages. It is possible a second unidentified material was also deployed."
All but two of the 117 hostages who died were killed by the mystery gas used by Russian special forces on Saturday to end a three-day siege. The two Germans were treated in a Munich university clinic and have since been released from hospital.
Russians have refused to identify the active agent in the gas used to stun bomb-laden Chechen rebels threatening to kill their hostages unless Russian troops withdrew from their southern homeland.
Russia says it is keeping the nature of the gas secret to avoid helping militants plan future attacks.