A gang raided a bar-cum-restaurant on Victoria Terrace from behind, while guards were patrolling the stretch in front, and decamped with Rs 3.9 lakh on Wednesday night.

A probe suggests the gang entered the restaurant, off Camac Street, by removing a part of the awning and broke the door leading to the cash box before emptying the till. No one has been arrested, but police suspect an insider had leaked information about the money in the cash box to the burglars.

“The employees downed shutters around midnight on Wednesday. When they turned up the next morning, part of the awning was removed and the cash missing. Nothing else in the restaurant was touched. Evidently, the gang knew the way to enter, where the cash box was kept and the sum inside,” said a senior officer of Shakespeare Sarani police station.

“We never leave behind such a huge sum in the cash drawer. But a day before, we had received a big payment from one of our clients and kept the money in the drawer. We are not sure if the information was leaked,” said an employee of the restaurant.

“The corner where the cash box is kept is separated from the rest of the eatery by a door that is not very strong. Since there had been no break-ins, the authorities did not bother to keep the corner well secured,” the employee added.

The police have called for experts to collect fingerprints and are also checking with the criminal records section for a lead.