The defence ministry has handed over a set of key documents to the CBI, including minutes of the meetings where the decision to purchase of three Embraer aircraft was taken, to help the agency in its probe into allegations that kickbacks were paid in the deal.
Though the deal was inked in 2008, the process had started much earlier.
Major decisions regarding the purchase of Embraer aircraft was taken at the Services level in 2006.
Then IAF chief S P Tyagi, who is under scanner in the VVIP chopper scam, did not respond to calls or messages on Whatsapp asking if he was aware of the role of middlemen.
It is expected that the CBI will reach out to all key officials who were part of the decision-making process.
The allegations of corruption in the deal surfaced in a Brazilian newspaper which alleged the Embraer had taken the services of middlemen to clinch the deal of aircraft supply in Saudi Arabia and India.
DRDO had purchased three aircraft from the Brazilian company in 2008 and customised them for air-borne radar system, known as airborne early-warning and control (AEW&C) systems, for the Indian Air Force.
The CBI team, which is probing the VVIP chopper scam, is also looking into the files sent by the Defence Ministry.
CBI sources said officials are going through the reference and any decision to start a probe in the matter will be taken soon after analysing all the documents.
If the agency is satisfied that it has enough prima facie evidence to initiate an FIR, it will start or else it might register a preliminary enquiry to gather enough material for registering a regular case, they said.
DRDO has already sought a report from the Brazilian firm, which said it has been looking into graft allegations over the last five years.