"Passengers have been asked to evacuate the plane, the drill is taking place right now," Hemendra Singh, spokesperson for the federal Central Industrial Security Forces, toldTurkish Airlines was targeted with a series of hoax bomb warnings in April and again over the weekend. This threat was found about three hours into the flight, a spokesperson for the airline said.Indian security forces said they were scouring the plane for signs of explosives. The flight will resume its journey to Istanbul if is given the all clear, the airline spokesperson said.The airliner was over the central Indian city of Nagpur when the pilot sent a message requesting an emergency landing and he was given permission to change course to Delhi, said Rajan Bhagat, spokesman for Delhi police.The plane was being inspected in an isolated area of the airport, Bhagat said.