The State Secretariat on Wednesday received a threatening call from a unknown person, who warned that he would kill Chief Minister K Rosaiah.
Following the threatening call, the police officials and bomb disposal squad were alerted, and tight security arrangements were made on all blocks of the Secretariat, particularly the C and D blocks.
The police are enquiring about the origin of the call and whether the call was made from a landline or a mobile phone.
However, officials are yet to confirm the place of origin of call.