A multi-tier security ring was thrown around each floor of the city hotel, where visiting US secretary of state Hillary Clinton is staying with a 40-member delegation, with elite US security personnel from the FBI entirely looking after the dignitary's security.
Starting from the reception counter to the upper floors, banquet hall and other rooms, FBI teams have taken over providing complete security, police sources said.
Nearly 100 rooms have been booked for the visiting US delegation.
The FBI teams arrived in the city at least a week back to review security for Hillary Clinton and her entourage.
Boarders have been issued special passes and everyone is being frisked before being allowed entry through the security zones.
Security has been stringent in the entire Alipore area where the hotel is situated as also around the Zoological garden and the National Library in the area.
Contacted, hotel authorities refused to speak about the menu for the former US first lady and requested the US consulate not to answer queries regarding this, sources said.
Sunday traffic in front of the Jawaharlal Nehru road was regulated as Clinton visited the Indian Council for Cultural Relations (ICCR) before her arrival at the Victoria Memorial.
Curious onlookers were kept at bay by the policemen as the motorcades of the high-profile visitor arrived at the venues during the day.
Meanwhile, the Writers' Buildings, the venue of the meeting between Banerjee and Clinton, has been converted into a virtual fortress and here, too, the security is being monitored as per the FBI teams' suggestions.
Last-minute touches are being given to the red-brick Raj-era building with the corridors and staircases spruced up and given a fresh coat of paint for the grand occasion.
A portrait of Rabindranath Tagore hung on a wall of the long corridor on the first floor was cleaned.
FBI teams had been frequently visiting the building for the past few days to advise the police on how to adhere to security norms for the visitor.
For the first time-ever, ministers have been requested to use the side gate of the secretariat for entry, as the central gate has been kept reserved only for the chief minister and the visiting former US first lady.
The FBI teams inspected the building for the fourth day on Sunday together with top city police officers and intelligence officials with special attention being paid to stairs and corridors through which the VVIP will pass.
A series of high-level meetings took place. A wooden partition was erected before the Press Corner and a metal detector placed to keep the overzealous newsmen at bay during the Clinton visit.
State government employees will have to enter the Writers' Buildings with special passes on Monday.
Strict instructions have been issued to ensure uninterrupted power at the building and the Fire Services Department asked to keep fire-tenders ready.
Clinton is scheduled to attend a programme with a cross-section of society at a premier educational institution in the city prior to the meeting with the chief minister.
She would leave for Delhi after meeting the chief minister.