The Kharabovsk-Neryungri train carrying around 400 people derailed at 8:00 a.m. Moscow time (04:00 GMT), while travelling at a speed of around 88 km/h (55 mph). Ten of the train's 16 carriages overturned, and around 60 people suffered injuries, five of whom are in hospital.
Oleg Safonov, the presidential aide to the Far East region, told RIA Novosti that the cause of the accident was "a double-buckling of a stretch of seamless rail due to temperature stress." Around 400 meters of track was damaged, he said.
The Transportation Ministry said: "The cause of the accident is being investigated. According to preliminary information, the driver, after navigating a leftward bend, saw a buckling in the track 200 meters away, while travelling at 95 km/h, and applied the emergency break. He brought the speed down to around 88 km/h."
Russian Railways said trains in the area are using an alternative line, and are facing delays of no more than one and a half hours. The section of damaged track is near the town of Shimanovsk in the Amur Region.
Company Vice President Vadim Morozov said: "We are doing everything possible to re-start traffic along this route as soon as possible."