An undertrial fled while being brought back to the city by train from Bihar, where he was produced in court, on Wednesday night.

Umesh Prasad Singh — escorted by a sergeant, an assistant sub-inspector and two constables — disappeared from the Danapur Express while the train was waiting to leave Patna for Howrah. He could not be found anywhere at or around the station.

“Let the team come back. The details (of the circumstances leading to Prasad’s escape) would be known after that,” said Jawed Shamim, the joint commissioner of police (headquarters). A case has been registered with the Patna GRP.

Singh, 40, is accused of robbing a bank in Watgunge in 2003 and was lodged at Presidency jail. He is also an accused in several other cases in various states, including Bihar. The police team left with Singh for Bihar on March 22 as a court in Danapur, near Patna, had summoned him.