CBI sources said the preliminary inquiry has been registered on the request of the Defence Ministry after it emerged that a Brigadier-level officer allegedly promised to help AgustaWestland swing the 197-helicopter deal.
He had allegedly demanded $5 million for the job.
The sources said Italian investigators, who are probing corruption allegations against AgustaWestland and its parent Italian firm Finmeccanica in that country, have found some documents which show that Indian army officer had allegedly demanded the bribe from the firm.
The information was provided to the defence ministry by the Italian investigators which forwarded it to CBI to look into the matter.
Finding prima-facie material to start investigations, the agency has registered a preliminary enquiry and might soon call the officer in question for examination.
The sources said they are going ahead with the preliminary enquiry as it needs to ascertain the nature of the crime, before proceeding with the registration of the case.
Army wanted to purchase 197-light utility helicopters to strengthen its Cheetah fleet but after the allegations of corruption surfaced, the deal has been hanging in limbo.
AgustaWestland was also embroiled in the bribery scandal involving former Indian Air Force Chief S P Tyagi and his cousins.
Tyagi, AgustaWestland, its parent company Finmeccanica are among the 13 accused in the CBI case regarding alleged payment of Rs 362 crore bribe to swing the 12 helicopter deal in favour of the Anglo-Italian company, CBI sources said.