UGLOVKA, Russia (November 28, 2009)--Russian investigators are considering whether a train derailment that killed at least 26 people was caused by a bomb on the tracks.

If so, it would be Russia's deadliest terrorist strike outside the volatile North Caucasus in years.

The Nevsky Express was carrying hundreds of passengers from Moscow to St. Petersburg when it went off rails Friday night.

Some officials say at least 26 people were killed and nearly 100 were injured and hospitalized, although the Prosecutor General's office said the death toll has risen to 30 while 60 people remain in the hospital.

Health Minister Tatyana Golikova said another 18 people are still missing from the disaster, which authorities are investigating as an act of terrorism.

Russian President Dmitry Medvedev is calling for calm.