Central Bureau of Investigation sources said a DIG Mahipal Yadav returned on from Milan where the trial against the then executives of Finmeccanica and AgustaWestland are being prosecuted by the Italian authorities for alleged international corruption.
India is being represented as civil party in the case by defence ministry.
They said CBI was expecting to get copies of transcripts of phone conversations of middlemen which were intercepted by the Italian agencies but it may take some time because of court's procedural issues.
The sources said a fresh tranche of documents have been handed over to the Indian mission on the orders of the Milan court but did not give their details as it might compromise their ongoing probe by the agency.
The sources said a set of over 40,000 documents related to contours of money trail has already been received by the CBI from the Italian court after defence ministry became a civil party in the ongoing case in the European country.
The sources said once CBI gets these records it might question Tyagi and other accused again before starting to prepare the charge sheet against the accused.
CBI which carried out probe in India had named 13 individuals, including Tyagi and European middlemen Carlo Gerosa, Christian Michel and Guido Haschke, in the FIR as accused, in connection with the alleged bribery.
Italian agencies had arrested the then CEO of AgustaWestland Giuseppe Orsi for alleged bribe given to Indian middlemen to clinch the deal.
The supply of 12 VVIP helicopters from AgustaWestland had come under scanner after Italian authorities alleged that bribe money was given by the company to clinch the deal.
The Italian prosecutor, who carried out the preliminary enquiry, alleged that the CEO of Finmeccanica, parent company of UK-based AgustaWestland, had used services of middlemen to bribe Indian officials in India.
The probe agency has alleged that during his tenure as the IAF chief, Tyagi and "with his approval" the Air Force "conceded to reduce the service ceiling for VVIP helicopters from 6,000 m to 4,500 m as mandatory to which it was opposing vehemently on the grounds of security constraints and other related reasons".
According to the FIR, "Haschke Guido and Gerosa Carlo (middlemen) managed to send Euro 5.6 million through Mohali-based IDS Infotech and Chandigarh-based Aeromatrix Info Solutions Private Ltd to India and kept the remaining amount out of about Euro 24.30 million received from AgustaWestland with themselves in the account of IDS Tunisia."
Both the Indian companies have denied involvement in the bribery scandal.
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