The CBI has filed its charge sheet against former NSE MD and CEO Chitra Ramkrishna and ex-Group Operating Officer Anand Subramanian in connection with its probe into a co-location scam case, officials said Thursday.

Ramkrishna and Subramanian are both in judicial custody following their arrest by the CBI on March 6 and February 25 respectively, they said.

In its charge sheet filed in their Special Court here, the CBI has alleged that Ramkrishna allegedly abused her official position in key decisions among other charges.

The SEBI on February 11 had charged Ramkrishna and others with alleged governance lapses in the appointment of Subramanian as the chief strategic advisor and his re-designation as group operating officer and advisor to MD.

Ramkrishna had told the regulator that a formless mysterious ‘Yogi’ was guiding her over emails in taking the decisions.

The CBI which expanded its probe in the co-location scam, after SEBI report surfaced, has arrested both of them and told the court that formless Yogi is none other than Subramanian who was alleged beneficiary of her decisions.

Ramkrishna, who succeeded former CEO Ravi Narain in 2013, had appointed Subramanian as her advisor who was later elevated as group operating officer (GOO) at a fat pay cheque of Rs 4.21 crore annually, they said.

Subramanian's controversial appointment and subsequent elevation, besides crucial decisions, were guided by an unidentified person who Ramkrishna claimed was a formless mysterious yogi dwelling in the Himalayas, a probe into her email exchanges during the Sebi-ordered audit had showed.

In her statement to Sebi, Ramkrishna had said that the unknown person having email id rigyajursama@outlook.com was a ‘Sidha-purusha’ or ‘paramhansa’ who did not have a physical persona and could materialise at will.

Ramkrishna got elevated as MD and CEO on April 1, 2013 and left the bourse in 2016.

It was during this period that co-location was started by NSE, the CBI has alleged in the charge sheet.

In the co-location facility offered by NSE, brokers could place their servers within the stock exchange premises giving them faster access to the markets. It is alleged that some brokers in connivance with insiders abused the algorithm and the co-location facility to make windfall profits.