Sources in the CBI said the agency, which is grappling with severe shortage of investigating officers, will wind up by July 31 its probe in the scam.
The agency has already named former telecom minister A Raja, DMK MP and daughter of Tamil Nadu Chief Minister Kanimozhi, Shahid Balwa and Asif Balwa of DB reality, Sanjay Chandra of Unitech, along with several telcom firms and bureaucrats as accused.
CBI has filed two charge sheets in the case in which it has slapped charges of forgery, cheating, criminal conspiracy and relevant sections of Prevention of Corruption Act against the accused.
"We will complete our probe by July 31. There will be two more charge sheets in the case," an official said. The agency lodged an FIR in the case in 2009 and the first charge sheet was filed on April 2, 2011.
The CBI director had recently said that the agency is facing shortage of around 30 officers and over 10,000 cases were pending in various courts.
The spectrum allocation scam is said to be one of the largest financial bungling in the country causing a loss of over Rs 50,000 crore to the exchequer, where second generation of scarce spectrum was given to various telecom firms.
It is alleged that the accused telecom firms, which bagged the spectrum at 10-year-old prices, sold their shares to other firms at a premium, thus earning massive profits by allegedly acting as front for telecom companies.