A union has called on a rail company to reconsider its position on train guards after carriages 'de-coupled' outside Leeds Station.
Forty passengers were evacuated from the service, but nobody was injured.
Mick Cash, general secretary of the RMT union, said: "RMT awaits the findings from the investigation into this potentially horrific incident but once again it demonstrates the need to have a guard on Northern Rail trains to deal with these emergency situations.
"What we do know is that there was a guard on board this service who was at the rear of the train with the full suite of safety competencies for exactly this kind of situation.
"What would have happened on a driver only service with no guard on board? Who would have ensured that the passengers were safely evacuated along the track?
"The threat to axe guards on Northern Rail should be lifted and lifted now."
RMT has been in a long-running dispute with rail companies about the role of train guards.
A spokesman for Northern, formerly known as Northern Rail, said: “We never compromise on the safety of our customers and staff.
“We are working closely with the RAIB (Rail Accident Investigation Branch) to investigate the incident and will address any issues raised as part of this process.
“It would be inappropriate to comment further until this investigation has been completed.”