Railway officials said the Delhi-bound train started its journey at 8.35 am from Darbhanga station and reached Laheriasarai at 8.45 am. Four coaches at the rear got unlinked when the train left the place, throwing the railway traffic out of gear.
"The railway officials called the next station Thalwara and 12565 Sampark Kranti was stopped there. The engine was sent back to retrieve the coaches left behind. We are investigating how the incident happened," said Samastipur railway division Public Relations Officer A A Humayun.