The coaches suddenly started moving on their own when they were in the washing line area and rolled backwards nearly 800 metres, he said.
No one has been injured in the incident and no rail traffic was affected, the official said.
"The standby coaches of the Shatabdi train were stationed in the yard. They rolled down suddenly and moved backwards to a distance of nearly 800 metres after which they were derailed. However, no one was hurt in the incident and no rail traffic was affected," R K Datta, Chandigarh railway station manager, said.
He said that senior officials from the Northern Railways, Ambala Division, had reached the spot.
A probe had been ordered and reasons would be ascertained which resulted in the incident. However, taking prima facie cognisance of alleged negligence on part of some officials who were supposed to secure the coaches, Datta said.
Two persons including a yard master had been suspended and further inquiry was on, Divisional Railways Manager, Ambala Cantt, A K Kathpal said.