Kolkata: Trinamool chief Mamata Banerjee‘s residence in Kolkata’s Kalighat and her office in Nabanna were placed under an unprecedented security lockdown on Monday, even as Bengal’s chief secretary Dushyant Nariala instructed all departmental heads to ensure no official documents are removed, damaged or copied without authorisation.Long before the final results of the assembly polls were declared, central paramilitary forces had ringed Nabanna and stepped up vigil outside the CM’s Kalighat residence, as well as at the home of Trinamool Congress national general secretary Abhishek Banerjee, by Monday afternoon.The deployment came amid celebrations by BJP supporters in parts of Kalighat and sporadic reports of tension in the state as trends showed Trinamool Congress was facing a rout.“All Departmental Secretaries and Head of Offices are requested to ensure that no important paper or any file is removed/damaged or otherwise taken out from the offices. No unauthorised copying/scanning shall be permitted. All files/important papers/communication shall be properly accounted for. The Head of Departments and Departmental Secretaries shall personally ensure that this is followed in letter and spirit,” the chief secretary’s order stated.Quick response teams were deployed at the main offices of key govt departments.Election Commission said the steps are purely preventive.