The anti-corruption unit II of the CBI, headed by S K Upadhyay, has sought more officials from other wings in the agency.
Some officials borrowed from other wings have already been pressed into the surveillance and search operations.
A middle-level CBI officer has already been posted last week at Sanchar Bhavan to help collect information from officials in the department of telecommunications (DoT).
CBI sources say the leads that have come out following the interrogation of ARM Ltd promoter Patalu Ramarao and suspended DoT official Runu Ghosh are being followed up by the agency which requires more investigating officers than those currently on the job.
Further, the scrutiny of documents seized from the raids and searches at the offices of Himachal Futuristic Communications Limited (HFCL), residence of its vice-president Mahendra Nahata, the office and residence of Radhey Shyam Khemka (said to be a close friend of Sukh Ram), and the examination of some others whose names have cropped up have required far too many persons that what are at present working with the anti-corruption cell II.
The investigating agency is receiving help from a former top DoT official in unravelling the mysterious telecom deals, sources said. The official is believed to have played a key role in helping the agency secure the documents relating to the multi-access rural radio deal with ARM Ltd. CBI has sought the help of more officials to get to the bottom of the mystery.
According to CBI sources, there is little possibility of Sukh Ram's visa being extended. The CBI is keen to see the former minister return to the country at the earliest.
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Among those on the watchlist of the premier investigating agency are at least three close friends of Sukh Ram, some of whom played a role in clinching telecom deals. One was examined by the CBI for a few hours last week, while two others have yet to be interrogated.
The statements of Runu Ghosh and Patalu Ramarao on details of the ARM and other deals are being compared so as to ascertain what exactly transpired at the ministry.
Officials say that additional details about the deal could be obtained after Ramarao had been questioned at length. "The details provided by Runu Ghosh have been of immense help," a CBI official said.
Sources said the details of five diaries, which reportedly contain the notings in the former minister's hand and which had been seized from his official residence during the raid, has yet to be completely deciphered.
Meanwhile, in a statement issued yesterday, HFCL executive director A Kharbanda said that denied newspaper reports of an improper nexus between Nahata and Sukh Ram.
"The inferences drawn in various newspaper items are not supported by any of the materials found at the office premises of HFCL or the residential premises of Nahata," the statement said.