The CBI has already registered a preliminary enquiry in the spectrum allocated during 2001-07 and recorded the statement of former Aircel Chief C Sivasankaran in which he is understood to have alleged that Maran had coerced him into selling his firm to a Malaysia-based businessman, agency sources said.
The agency is likely to register a case in spectrum allocations during the period spanning 2001-07 by first week of July, they said.
"The CBI is looking at all the aspects of spectrum allocation during 2001-07 through a preliminary enquiry. But it will register a case only after seeking clarification from all persons under scanner which includes Dayanidhi Maran," an official said on the condition of anonymity.
Sources said the statement of Sivasankaran may not be the only basis for quizzing Maran.
He may also be asked to clarify questions regarding spectrum allocation as he was a telecom minister during the period to which the ongoing enquiry pertains to, they said.
Former telecom minister Arun Shourie, who held the charge between 2003-04, has already been questioned by the CBI on February 25 in detail about the allocation of telecom airwaves during his tenure but the agency "so far" has not found anything against him, they said.
The agency has registered a preliminary enquiry against "unknown persons" on Supreme Court's directive to detect any alleged anomaly in ''first-come-first-served'' of Cabinet during spectrum allocation between 2001-07.