The Rajendra Nagar-Guwahati Capital Express derailed at Samuktala Road station in Alipurduar district on Tuesday night, North East Frontier Railway Chief Public Relation Officer (CPRO), Pranav Jyoti Sharma, said.
The injured persons were identified as Indrajit Mandal, 25, Parikshit Mandal, 40, Pritam Mandal, 16, Rupa Mandal, 34, Shah Jamal Sheikh, 35, and Surender Prasad, 38.
"The deceased are yet to be identified. The injured were treated by railway doctors who reached the site soon after the accident," Sharma said.
He said the unaffected portion of the 19 coaches train was detached.
The train resumed its journey around 5.10 a.m. on Wednesday morning.
At least three trains were cancelled, two short terminated and eight trains were diverted following the accident.