A crack in the tracks prima facie caused the derailment of eight coaches of Mahakaushal Express near Mahoba station in Uttar Pradesh on Thursday.
Speaking on the sidelines of a function, Minister of State for Railways Manoj Sinha said that "according to the Divisional Railway Manager, prima facie fresh weld failure on left side caused the derailment."
Fresh welding means it was not an old crack and that the crack developed suddenly and could not be detected.
While the UP ADG (Law and Order) Daljit Chaudhary said 52 passengers were injured in the mishap, Sinha said 21 were injured, including one seriously.
The derailment took place near Mahoba station in Uttar Pradesh.
The DRM of Jhansi Division and General Manager of North Central Railway have rushed to the site after the accident to supervise the rescue and relief operations.