Authorities believe the group rented a space next to the Bank of Baroda so they could dig the tunnel.
It is not a scene from a movie or some television series but a real-life incidence where some thieves dug a tunnel under a Navi Mumbai bank, broke into 30 lockers and stole valuables worth Rupees 5-6 crore, police said.
The theft came to light on Monday when the bank staff went to the locker room and found it in complete disarray, with numerous lockers still open.
They are said to have run a grocery shop on the premises to provide cover for their activities.
The total value of the stolen goods is not yet known, as the police are still recording the statements of the bank customers.
The bank has closed-circuit television (CCTV) cameras, but none inside the locker room.
"The culprits made a tunnel from the adjacent gaala [shop] and entered the locker room". A horizontal tunnel of around 30 feet with a height of around four-and-a-half feet was dug to a spot under the bank locker room.
The police have formed 10 teams and have sent their officers to different places looking for the criminals.
Officials said that about 237 lockers, 30 lockers were found open. The bank had called all its customers to following the robbery for assessment of the robbery.
The incident was reported when the bank was reopened on Monday where its staff found several lockers in the treasury room was damaged. In most other cases, bank locker facilities are said to be "unavailable" for regular customers. Speaking to the press, DCP Sudhakar Pathare, Zone I, Navi Mumbai Police, said,"We have registered an offence in Sanpada police station under Section 454, 457 and 380 of the IPC,"said Hemant Nagrale, Commissioner of Navi Mumbai Police".