48-year-old Maran was questioned for nearly eight hours at the CBI headquarters by the agency's Special Task Force which is handling the investigation, CBI sources said.
Maran refused to take questions from waiting reporters and left. He had been called on Monday but did not turn up and approached the Madras High Court for interim anticipatory bail, which was granted to him yesterday.
CBI has alleged that 323 lines were installed in the name of BSNL General Manager connecting the Boat House residence of Maran with the office of the family-run Sun TV through a dedicated underground cable during his tenure as Telecom Minister.
Sources said these were not ordinary telephone lines but costly ISDN, capable of carrying huge data, to facilitate faster transmission of TV news and programmes across the globe.
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CBI had in its report to the Telecom Secretary alleged these lines were for use by large commercial enterprises to meet special needs such as video conferencing or transmission of huge volume of digital data for which heavy fee is charged but Sun TV got it for free.
The illegal telephone exchange has been cited by the Home Ministry as one of the reasons for denying security clearance to the Sun TV network. The Ministry has said it posed a serious threat to national security.
An Economics graduate from prestigious Loyola College, Maran was telecom minister from May 2004 to July 2007. He was Textile Minister during UPA II but had to quit after his alleged role in spectrum allocation scam case surfaced. He has already been chargesheeted in Aircel-Maxis case, an offshoot of 2G spectrum scam.
Sun TV is owned by Maran's borther Kalanithi.