CBI sources said the agency has received partial responses from Mauritius, Tunisia, Italy, British Virgin Island, the UK and Switzerland.
However, responses on its request from Singapore and the UAE were still awaited and both the countries have been approached through diplomatic channels for expediting the Letters Rogatory sent in the case, the sources said.
As part of its investigations, the agency is focussing on the money trail of suspected kickbacks of over 50 million Euros (about Rs 369 crore at present exchange rates) believed to have been moved across eight countries.
Last week, the CBI arrested former IAF chief S P Tyagi, his cousin Sajeev Tyagi and lawyer-businessman Gautam Khaitan regarding a case registered against 14 people including European middlemen in connection with alleged bribery in the 2010 deal of 12 AgustaWestland helicopters for VVIPs.
The allegation against the former Air Chief was that he reduced flying ceiling of the helicopter from 6,000m to 4,500m (15,000ft)which put AgustaWestland helicopters in the race for the deal without which its choppers were not even qualified for submission of bids.