The Indian Ministry of Defense has asked the country's premier investigating agency -- the Central Bureau of Investigation (CBI), to probe the alleged leak of question papers for the army's recruitment exam, officials said Thursday.

The leak of papers detected by police in western state of Maharashtra on Sunday led to cancellation of the exam for entire Pune zone.

India's official broadcaster - All India Radio (AIR)-- said Defense Minister Monohar Parrikar gave his nod after army recommended for investigation into entire incident by the agency.

Police has arrested 18 people for their involvement in the case and questioned over 300 candidates.

According to police, the candidates appearing in the recruitment exam were given the question papers in advance by people involved in the leak.

Reports said examination at other centres might also be cancelled in wake of the leak.

The examinations were held on Sunday for lower-level posts including those of soldier clerk, strongman and soldier tradesman across India.

Indian army has already initiated an internal court of inquiry into the case.

Source: Xinhua