Meanwhile, the CBI is also likely to question Congress MP Vijay Darda's son Devendra this week in connection with a separate coal block allocation scam probed by the agency.
The CBI had alleged in its FIR that after getting the coal block in Odisha by misrepresenting the facts, promoters of the company made huge profits of Rs. 200 crore by selling their stake to Essar Power and its subsidiary company.
Essar Power is not named as accused in the CBI FIR. The company had rejected the allegations, saying its acquisition of Nava Bharat Power Pvt Ltd (NPPL) was "transparent" and NPPL was never its front company.
The sources said the duo were questioned at length about sale of stake to Essar Power to which they said that souring relations between them were primary reason for selling it.
They were grilled about the company's relations with Globeleq Singapore and Suez International. At different stages of screening process, they had allegedly claimed that it was supported by these firms to inflate its net worth.
The CBI alleged that the coal ministry had kept a minimum net worth of Rs. 50 lakh per mega watt of the maximum capacity of the proposed power plant as a pre-qualification criteria.
The FIR alleged that the company with a proposed capacity of 2240 MW would not have pre-qualified for the recommendation of the Ministry of Power but for this deception.