The CBI has sought details from the Department of Telecom about the alleged illegal allocation of over 300 telephone lines to the residence of Dayanidhi Maran in Chennai which were linked with a television channel owned by his brother.

The agency which started the probe in the matter last week after registering a preliminary enquiry has sought documents related to sanction given for setting these ISDN lines which are capable for carrying huge amount of data.

The CBI has asked the Telecommunication Department to provide them with technical details of the alleged set-up connecting Sun TV office and former Telecom Minister Dayanidhi Maran''s residence.

Nearly four years after getting complaints, the CBI has started a formal probe into allegations that a 'virtual' telephone exchange was set-up at the then Telecom Minister's for facilitating data transfer from Sun TV owned by his brother.

These 323 residential lines were in the name of BSNL General Manager connecting the Boat House residence of Maran with office of Sun TV through a dedicated underground cable during the tenure of Maran as Telecom Minister, sources in the CBI claimed.

The agency recommended action in the case to Telecom Secretary in 2007 but the department allegedly did not give its nod, the sources said.

The CBI has alleged that these lines, used by medium to large commercial enterprises to meet special needs such as video conferencing and transmission of huge volume of digital data, for which a heavy price is to be paid, were almost free for Sun TV through this set-up.

It said that this virtual exchange was programmed in such a way that except "authorised BSNL staff", no one in the state-owned telecom company was aware of its existence.

The CBI alleged that a stealth cable was used to connect the residence of the Minister with Sun TV office to give impression that these lines were for the Minister but actually they were used by the channel.