CBI is scrutinising crucial documents received from Bharat Sanchar Nigam Limited (BSNL) on allocation of over 300 high-capacity telecom lines to former Telecom Minister Dayanidhi Maran's residence that were allegedly used by a private channel owned by his brother.

Sources said the scrutiny will take another two months after which CBI will be filing a regular case in the matter.

The agency had sought these documents from the state run telecom firm after filing preliminary enquiry in the case.

The sources in the agency said they were trying to figure out how the allocation of such a huge number of ISDN lines capable of carrying very large data was made to Chennai residence of the former Telecome Minister and how was it connected to Sun TV Channel office.

They are also trying to analyse the losses suffered by the operator because of these dedicated lines.

The agency had 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 Kalanithi Maran.