Ten lockers of a nationalised bank, which did not have a night guard, were broken into late on Sunday night at Mugma, 35km from Dhanbad district headquarters.

Bank of India manager Shambhu Nath Ram discovered the burglary on Monday morning at 10am, when he saw the locker room and a rear window of the building broken, empty jewellery boxes and purses strewn on the ground. The bank manager informed Nirsa police.

From the evidence, it appeared a gang entered the double-storey bank building from the rear window of the ground floor.

They first snapped the CCTV camera and bank alarm wires and entered the strongroom in an attempt to loot the cash safe.

Failing to prise open the safe, they broke into the locker room, cutting 10 of the 55 lockers open with gas cutters in a hurry.

Stuffing the jewellery, they left the bank noiselessly.

As no night guard was deputed at the bank, no one noticed the incident.

Police have not yet arrived at the quantum of jewellery and valuables burgled as all the owners could not be contacted, said Nirsa police station officer-in-charge (OC) Rampravesh Singh.

"The calculation of valuables lost would be estimated only when all 10 victims furnish their lists. So far, only a couple of customers have arrived," he said.

OC Singh also told The Telegraph that bank authorities had displayed gross negligence.

"An easily opened rear window on the ground floor and no night guard made the job easy for burglars," Singh said. "A policemen is deputed at the bank during the day. In March, we had written to the bank manager to depute a night guard. Bank authorities failed to take timely and most necessary step to safeguard its valuables," he added.

At the moment nothing conclusive could be said about whether a local gang or outsiders were involved in the burglary, the OC said.

"We are investigating the issue from all angles. The criminals will be arrested soon," he said.