Instructions to this effect are expected to be sent out in a day or two to the exchanges. The regulator is also seeking information on top 20 buyer and seller brokers at all the exchanges, including BSE and NSE. The rationale behind seeking information on the top 20 buyer and seller brokers at each bourse is to find out whether Mr Rathi or those who were present in his room at the time when he made the controversial call to the surveillance department of the exchange put through trades using other brokers spread across regional exchanges as fronts or conduits. "If we find any abnormal trends in these transactions, we will then seek details of their (the brokers') clients," a Sebi official said.

As reported earlier, the Rathi tapes probe has reached a decisive phase, with the regulator now armed with two sets of tapes - one containing the conversation between Mr Rathi and a surveillance department officer and the other containing conversations among four officials of the BSE's surveillance department. These officials are Mr Arun Dhanawade, Mr AA Tirodkar, Mr Sanjay Pardiwala and Mr PS Reddy. Mr Rathi has, however, claimed he did no wrong by talking to the surveillance department since he was the BSE president and well within his rights to do so.

The tapes controversy has also taken a new twist with Sebi investigations chief LK Singhvi moving out of the tapes part of the probe and executive director CM Mehra coming in his place.