[18] The government confirmed that the accident was caused by terrorists, making this attack Russia's deadliest outside the North Caucasus region since the 2004 Russian aircraft bombings.

[18] Later on 28 November, Alexander Bortnikov, head of the Federal Security Service (FSB), reported to President Dmitry Medvedev that the train was derailed by an explosion of 29.288 MJ.

While some reports indicated suspicion of terrorist-related activities, one law enforcement official said that the crater "must be just a pit someone dug out [or could have been] left by an explosive device".

[23][24] Responsibility for the attack had first been claimed by far-right nationalists,[25] then by the "Caucasian Mujahadeen" on orders from Dokka Umarov, who is considered to be "the leader of the Islamist insurgency in the North Caucasus.

[34] In a televised Q&A session on 3 December, Prime Minister Vladimir Putin also called for tough measures against the perpetrators of the bombing and reiterated terrorism still caused significant threats to the country.

Russian Security Services allege these individuals had rented a house in the nearby village with a purpose of establishing train movement schedules for planning the attack and subsequently planted the explosives.

[36][37] On 31 March 2010, the official investigation resulted in charges of terrorism, participation in unlawful armed formations and illegal trafficking in explosives and ammunition against 12 ethnic Ingush from the village of Ekazhevo in Ingushetia; 11 of them have the last name Kartoyev and are related; the 12th is Zelimkhan Aushev.