New Delhi, June 1 (IANS) Prime Minister Manmohan Singh will not be probed for alleged irregularities in the allocation of coal blocks between 2006 and 2009, the CBI said Friday.

The Central Bureau of Investigation has launched a preliminary inquiry into the alleged scam.

According to official sources, the probe agency will scrutinise two aspects - misuse of allocation of coal blocks and misuse of coal blocks by private companies.

The agency will scrutinise 156 companies and 65 coal blocks, said a CBI source.

The CBI has started verifying the allegations of irregularities in the allocation to private companies between 2006 and 2009 and their alleged misuse.

The CBI has been asked by the Central Vigilance Commission (CVC) to probe the complaints related to alleged losses to the public exchequer in allocation of coal blocks.

The CVC directive followed a complaint by Bharatiya Janata Party (BJP) MPs Prakash Javadekar and Hansraj Ahir, who have said the prime minister headed the coal ministry when most allocations were done.

Earlier, a draft report of the Comptroller and Auditor General (CAG) had stated that the government's decision not to auction coal blocks caused a loss of Rs.1.8 lakh crore to the public exchequer.