Kolkata: A phone call on Thursday claiming that a bomb had been planted inside the West Bengal secretariat 'Nabanna' that houses Chief Minister Mamata Banerjee's office, turned out to be hoax.

The call was received at the PBX of 'Nabanna' when the Chief Minister was present in her office on the 14th floor. Police was immediately informed of about the phone call, Joint Commissioner Kolkata Police (Headquarters) Supratim Sarkar said.