India News: The Central Bureau of Investigation (CBI) is all set to quiz the top guns of the Prime Minister's Office (PMO) in its Coalgate scam probe.

According to report officials likely to face CBI questioning include TKA Nair, who was principal secretary to Prime Minister Manmohan Singh in 2009 when he also handled the coal portfolio. Nair, a former IAS officer of the Punjab cadre, now holds the rank of a minister of state in the Prime Minister's Office.