A far-right neo-Nazi group claimed the attack on a Russian train traveling from Moscow to St. Petersurgo that killed 26 people.

Investigators confirmed that a powerful improvised bomb caused Friday’s devastating train crash in which at least 26 people, including several top government officials, were killed.

The head of Russia’s FSB counter-terrorism agency, Alexander Bortnikov, said the bomb, hidden on the railway line between Moscow and St Petersburg, contained the equivalent of 7kg (15.4lb) of TNT. Officers had found “elements of an explosive device”, he said.

Today two huge cranes lifted up wreckage at the crash site as workers searched for the missing. Officials said 18 people were still unaccounted for. Nearly 100 people injured in the crash were being treated in hospitals.

The Echo of Moscow radio station reports that the neo-Nazi organization Combat 18 has claimed responsibility for the incident. However, analysts contacted by other Russian media say the neo-Nazi claim is not credible and may just be a publicity attempt.