PESHAWAR: Feb 20 (INP) The National Accountability Bureau on Tuesday commenced a probe into the Pakistan Tehreek-e-Insaf (PTI) Chief Imran Khan's use of provincial government's helicopters. Imran, on February 3, had said that the KP government had clarified that there was never any personal or private use of government helicopters by him. He also welcomed the examining of the issue by NAB. INP/AH