The agency has registered a preliminary enquiry into sale of telecom spectrum during 2001-07.
Sources in the agency said Standard Chartered was the banker in the deal in which Maxis bought 74 per cent stake in Aircel. They said documents from the bank could provide crucial details about the financial transactions.
They said officials of the bank's corporate wing were quizzed by CBI officials.
Sivasankaran had alleged in a statement before the agency that he was forced to sell his stake in Aircel by Maran and his brother Kalanidhi at a very cheap price to Malaysia-based Maxis, which is considered closed to Marans.
The allegations have been refuted by Dayanidhi who maintains that he did not play any role in the Aircel-Maxis deal.
Sources said the CBI primarily wants to get details of correspondence of bank with both parties -- Sivasankaran and Maxis officials and the manner in which entire deal was done.
CBI in the Preliminary Enquiry is verifying the allegations levelled by Sivasankaran and seeking documents and other details from Standard Chartered officials are part of that exercise, the sources said.