At least three persons were seriously injured when Arunachal Express derailed at Dubia in Assam's Sonitpur district on Friday.
Three bogies and engine of the train, travelling from Rangiya in Assam to Mokokcheleng in Arunachal Pradesh, derailed at 10.30am, Northeastern Frontier Railway chief public relation officer S Hajong said.
"We are ascertaining the cause of the derailment and a rescue team is at the spot to help the passengers," he told PTI.
Train movement in the section have been suspended and work was on to repair the damaged track, he added.
Ruling out any extremist involvement in the derailment, Sonitpur district superintendent of police A P Tiwari told PTI that it was due to mechanical fault.
Sonitpur district is affected by Bodo extremism.
The injured have been admitted to Kanaklata civil hospital.