At least 21 people were killed and 55 injured when the Nevsky Express train bound from Moscow to St. Petersburg derailed in what could be a terrorist attack, Russian emergencies and railroad sources reported Saturday.

An emergencies source said: "Twenty-one bodies have been found."

"The reasons for the accident are being established. One of the versions is that [the train was] blown up," the Russian Railways (RZD) monopoly said.

Power outage on the railroad is also considered a possible reason for the accident that saw several cars of the train go off the tracks.

RZD President Vladimir Yakunin is on his way to the accident site. Ambulances, Federal Security Service officers, law enforcers, emergencies services and railroad specialists are already at the site.

"Thirty injured passengers have been sent to [hospitals in] Bologoye, Alyoshinka and Borovichi," RZD said. "Another 20 injured were sent to Uglovka."

Two Emergency Situations Ministry aircraft were earlier reported heading to the accident site carrying equipment for a mobile hospital to render medical assistance to injured passengers.

RZD also said trains will move along a bypass route after the accident to keep railroad communication between the two largest Russian cities running.

MOSCOW, November 28 (RIA Novosti)