The Hyderabad international airport was on Friday put on high alert after an anonymous letter threatening that explosives will be used and transported through a flight was received at the facility.

Sources said the Chief Airport Security Officer of the sprawling complex received the letter which threatened that “explosives” will be used and transported through a flight which may take-off or land at the airport. The letter was received at the airport a day after Parliament approved a historic bill to carve out Telangana out of Andhra Pradesh amid vociferous protests by members from Seemandhra region as also from Trinamool Congress and Shiv Sena.