In the Bihar train disaster on June 6, 1981, a passenger train carrying 800 or more passengers between Mansi and Saharsa, India derailed and plunged into the river Bagmati while it was crossing a bridge.
After five days, more than 200 bodies were recovered, with hundreds more missing that were feared washed away by the river. Estimates of total deaths range from 500 to 800 or more. The accident is among the deadliest-ever rail accident on record.
The cause of the accident is uncertain as there are multiple causes listed online: