The robbers entered the UBI's Pashupati Nagar branch in Naubasta and disabled the CCTV cameras. They looted cash and jewellery worth crores, Senior Superintendent of Police (SSP) Akhilesh Kumar said.
They entered the bank by drilling a wall adjacent to a vacant plot and breaking a window. One of the cameras caught the robbers entering the bank before it was disabled, the SSP said.
The robbers used a gas cutter to open 32 of the bank's 220 lockers and cut the lock of the bank's main entrance, Mr Kumar said.
"They also tried to break the cash strong room, but failed. It seems the robbers spent hours in executing their plan," the SSP said.
The loss is being evaluated and forensic experts have been pressed into service, the SSP said, adding that a special task force (STF) led by Additional SP Vishal Vikram Singh is investigating the case.
Station House Officer, Naubasta, Akhilesh Jaiswal, was shunted from his post and was attached with the reserve police lines for dereliction of duty, the SSP said.