The Central Bureau of Investigation (CBI) will soon summon prime minister Manmohan Singh's advisor T K A Nair, to record his statement in the coal blocks allocation scam.
CBI had earlier summoned the accused former coal secretary H C Gupta and quizzed two former PMO officials - Vini Mahajan and Ashish Gupta - in connection with alleged irregularities in the allocations made during 2006 to 2009.
The two bureaucrats were posted in the prime minister's office when the coal blocks were allotted to private firms at nominal prices.
CBI is reported to have sought details of some coal fields that were allotted to private firms between 2006 and 2009, when Manmohan Singh held direct charge of the coal ministry.
TKA Nair has chaired the screening committee that clears coal block allocations several times in the past.
Mahajan, a 1987-batch IAS officer from Punjab cadre, was a director with the PMO during the period and has now been repatriated back to the state where she is principal secretary level officer.
Gupta, an IPS officer of the 1989 batch from Uttar Pradesh cadre, who was the vigilance officer in the PMO, has also gone back to his cadre.