MOSCOW, Aug 14 (Reuters) - Russia has launched a terrorism investigation into the derailment of an express train that injured dozens, a local official from the prosecutor-general's office said on Tuesday.

"The train accident was caused by a homemade explosive device," Sergei Bednichenko, a local prosecutor at the scene, was shown saying on Channel One television station.

"A criminal case has been opened under article 205, clause 3, that is terrorism," he said.

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