The Central Bureau of Investigation (CBI) on Saturday registered a Preliminary Enquiry against unknown officials of the Defence Ministry in connection with the allegations of corruption in the purchase of three Embraer aircraft in 2008.

"The Preliminary Enquiry has been registered on a reference from the Defence Ministry. The contracts include the one with the Defence Research and Development Organisation (DRDO) in 2008," said a CBI official.

It has been alleged that the Brazilian supplier had taken the services of middlemen to strike deals for sale of aircraft in India and Saudi Arabia.

The DRDO had signed a $208-million deal with Embraer for three ERJ-145 aircraft to build indigenous Airborne Early Warning and Control Systems for the Air Force.

A joint committee, set up the Air Force and the DRDO, had shortlisted Embraer for procurements after evaluating several options.

Following the allegations, the DRDO has sought an explanation from Embraer on the issue.

The Defence Ministry, which had asked for a probe by the CBI and the Enforcement Directorate (ED), has also written to the Ministry of External Affairs to pursue the matter with the respective countries through Indian missions.