The Rail Accident Investigation Branch (RAIB) is investigating after a passenger became trapped in train doors and dragged a short distance at Newcastle Central Station.
It happened on 5 June 2013 on a Transpennine Express service from Newcastle to Manchester Airport.
It was reported to the RAIB on 3 July.
The doors were closing as the passenger reached the train, so she put her hand between them, expecting them to re-open.
The doors continued to close around her wrist.
The train then started to move, forcing the passenger to walk and jog alongside.
The conductor, who was leaning out of the rear cab window, could not see the trapped passenger due to the curvature of the platform.
Passengers on board the train noticed what was happening and pulled the emergency door release which automatically applied the brakes.
The train moved less than one coach length and the passenger was able to remain on her feet, receiving minor injuries.