Eight coaches of the Agartala-Lokmanya Tilak Terminus Express derailed at Dibalong station in Assam's Dima Hasao district on Thursday afternoon, Northeast Frontier Railway officials said.
There were no reports of any fatality or major injuries yet, they said.
The cause of the derailment, which occurred at 3.55 pm, was yet to be ascertained.
The derailed coaches include the power car and the engine of the train.
An accident relief medical train has already left for the site from Lumding along with senior officers to supervise the rescue and restoration work.
Running of trains on the Lumding-Badarpur single-line hill section has been suspended, the officials added.
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