The search for survivors of an express train crash in Russia continues amidst suspicions of a terrorist attack.

The Moscow – St. Petersburg Nevsky Express, with 663 aboard, derailed around 9:30 pm Friday near the village of Uglovka about 200 miles north of Moscow.

Reports about the number of fatalities and injuries are conflicting.

Earlier local media reports listed the number of dead at 39 while the injured are reported anywhere between 60 and 96 listed at hospitals. 18 are reported missing.

Russian government officials, however, scaled the death toll down to 25 people.

In the meantime, speculations that the derailment might have been caused by a bomb blast are mounting, triggered by a small crater at the scene of the crash.

The cause of the derailment is under investigation.

"Several versions are being considered. It must be just a pit someone dug out. Or the crater was left by an explosive device," a law enforcement official is quoted by the Russian ITAR-TASS as saying.

Witnesses heard a loud bang before the crash, while the last four cars of the train have been fully destroyed, Russian media informs

The Russian media outlet Gazetta.ru reports that a member of the Movement against Illegal Immigration said he is responsible for the incident and the attack was conducted in the name of the far-right, nationalist Russian Combat 18. Gazetta.ru, however, points out that the authenticity of the statement remains unclear.

The Bulgarian Embassy in Moscow had not received information about Bulgarians being among the passengers on the ill-fated train.

In 2007, a bomb on the same line derailed a train, injuring nearly 30 passengers.