CBI has recommended to the defence ministry blacklisting of six firms, including four from abroad, as a sequel to its probe into the Ordnance Factory Board scam.

Official sources said the CBI is its letter has mentioned four international firms--Singapore Technologies Kinetics Ltd (STK), Israel Military Industries Ltd (IMI), Rheinmetall Air Defence (RAD), Zurich and Cooperation Defence in Russia.

Besides, two Indian firms--T S Kisan and Company Pvt Ltd (New Delhi) and R K Machines Tools Ltd (Ludhiana) have also been named in the CBI communication to the defence ministry sent earlier this week, they said.

The CBI in its chargesheet filed in Kolkata last month initially named only the two Indian firms and there was no mention of the foreign companies.

"The names of the (foreign) firms came up during the course of investigation. While two(indian firms) have been chargesheeted, the CBI letter also mentions four international companies whose name cropped up during the probe," a source said.

The letter is advisory nature and it is up to the defence ministry to accept the recommendation or not, the source said.

CBI had in June filed a 2,700-page chargesheet in a special CBI court in Kolkata against former Director General of Ordnance factory Board, Sudipta Ghosh and 11 others for graft.

A case was registered by CBI on May 17, 2009 under different Sections of IPC and Prevention of the Corruption Act against Ghosh and others.

It was alleged that Ghosh had entered into criminal conspiracy with other accused with the object of demanding and obtaining huge illegal gratification in the matter of various supply orders placed by Ordnance Factory Board (OFB) and also in the matters relating to transfer or posting of the officers of Ordnance Factories.

The chargesheet has named Ghosh and his wife Kajal Ghosh, Ramesh Nambiar, then additional GM (Sports) Air India, J K Thapar, director of T S Kishan and Companies Private Ltd, Satish Mahajan, director and Sunil Handa, manager of R K Machines Tools Ltd, Ludhiana.

Former statistical investigator of National Sample Survey Organisation, J K Grover, two private firms T S Kisan and Company Private Limited and R K Machines Tool Limited, chairman of Mokul Group of Companies Mohinder Singh Sahni and two private persons--Ashish Bose and Pradeep Rana--were also named in the chargesheet.

The matter will come up in the CBI court on July 31.