Defence consultant Sanjay Bhandari was raided by income tax department.
A number of middlemen and agents involved in defence deals have come under the scanner of security and investigative agencies afresh as part of their probe into a well-oiled machinery in the critical sector, with the governing pushing for a clean-up.
Sources said detailed dossiers are being prepared on several "suspicious" people connected to the defence sector.
The first to face the heat was defence consultant Sanjay Bhandari who was raided by the Income Tax department after being under surveillance, they said.
Certain documents seized from his possession led various agencies to a number of individuals who were subsequently put under the scanner, the sources said.
They alleged Mr Bhandari, who is said to have worked for a number of European firms, "enjoyed good connections" with government officials.
His call data records have revealed that he was in touch with a lot of other such "consultants", foreign companies and influential people.
While sifting through the documents, the agencies stumbled upon his links with another consultant who is very active in the aviation industry.
He too was searched by the Income Tax department soon after, but in connection with another case, and the effort now is to build data of common contacts in politics and bureaucracy, the sources said.
The Enforcement Directorate has issued notices to firms linked to Indian national Sudhir Choudhrie in connection with its foreign exchange violations probe in a 16-year-old case relating to alleged payment of kickbacks for providing field guns to the army and certain other defence deals.
Mr Choudhrie was investigated in 2004 by CBI over suspicions related to alleged pay-offs to him by a Russian company and UK firm Rolls Royce.
He has been on the radar of agencies for many years even though the CBI probe against him in two separate cases was closed.
Besides the central security agencies, other agencies keeping a tab on such consultants are the Income Tax department and the Enforcement Directorate.
"The aim is to gather as much information as possible about the network and once firm evidence crops up, the penal ball will be set rolling," a source said.