Russian officials believe the train disaster that killed dozens and injured nearly 100 was caused by a bomb.In a televised meeting, the head of the FSB domestic intelligence service told the President Dmitry Medvedev that Russian detectives had found fragments of what they suspect was a bomb. Criminal experts suggested from preliminary findings that the equivalent of 7kgs of TNT was detonated. Prosecutors have started a criminal case on charges of terrorism and possession of explosives. So far, no one has publicly claimed responsibility for the suspected attack. The Nevsky Express was derailed around 9pm local time 350 km north of Moscow Around 700 people were on board, 18 of which were still missing. Russian officials were working hard to clear the site and to unblock the main trainline between Moscow and Russia’s second city, St Petersburg.