At the same time, he confirmed the fact that a terrorist act was the most plausible theory. The blast occurred between the Paveletskaya and Avtozavodskaya stations.
The FSB warned mass-media bodies against preliminary speculations on the tragedy. One should not incite panic and hysteria, the FSB spokesman noted.
Criminalistics experts are now working at the scene. Preliminary investigation must be completed, because this is the only way to ascertain the explosion's causes, RIA-NOVOSTI interlocutor said.