Burglars sneaked into an income-tax building on Rafi Ahmed Kidwai Road, in central Calcutta on Sunday, broke into the chambers of two senior officers and left with the cabinets of two computers.

They did not touch anything else, but escaped with the computer cabinets that are loosely referred to as the Central Processing Unit (CPU) and contain the data-storing hard disks.

According to an officer of Park Street police station: ?Both the hard disks stored important and secret data?.

The theft was detected on Sunday night. ?The office on Rafi Ahmed Kidwai Road was closed. The caretaker had gone to the market around 6 pm. He returned after an hour and found the lock of the entrance broken,? said Anuj Sharma, deputy commissioner of police (headquarters).

Upstairs, the caretaker discovered that the locks of the rooms of two officers ? a commissioner and an assistant commissioner ? had also been broken.

Police said the nature of the theft suggested it could be an inside job. ?The burglary took place between 6 pm and 7 pm, when the caretaker had gone to the market. It appears, the burglars knew about this,? said an officer.

Detective department officers, who visited the office on Monday, said the burglars had taken away the monitor and the CPU from the office of B.S. Sandhu, commissioner of Indian Revenue Service.

?The burglars had not touched the computer monitor of assistant commissioner J.K. Sharma, in the adjoining office. But they had walked away with the detached cabinet,? said an officer, adding: ?They had not touched any other computer on the tables of the other departments.?

Police are sure the burglars had only targeted the hard disks.

?They did not touch any other equipment,? said an officer. ?It takes at least 10 minutes to take out a hard disk from a cabinet. The burglars did not want to take the risk of staying there for half-an-hour to detach two hard disks. So, they left with the CPUs.?

Police are sure that whoever had committed the crime had a basic knowledge of detaching computer cables connected with the monitor, CPU and keyboard.

Asked why the burglars did not take away a single monitor, an officer replied: ?It seems that they wanted to set up a complete configuration and examine what was stored in the hard disks.?