While Sebi has not named the exchange, media reports have said that one particular trading member once accounted for about 80 per cent of trading volume on United Stock Exchange, the country's newest bourse that began operations in 2010.

The issue came up for a discussion at Sebi's board meeting on November 24, 2011, the agenda and decision notes for which have been now released by the regulator.

As per a decision note on Sebi's surveillance action memorandum submitted that day, "The Board was apprised of the developments in the currency segment with regard to the abnormal concentrations of some trading members.

"The Board was also informed that Sebi had taken up the issue with the relevant Exchange and the matter would be brought to its logical conclusion shortly," it added.

While there have been no official words so far, the speculations have been rife that the USE's trade volumes have fallen in recent months mainly because of an ongoing Sebi probe into the state of affairs at the bourse.

There have been reports about a conflict of interest and a possible breach of fair-trade practices at the USE due to one of its largest shareholders, Jaypee Capital, also being a major trader on the exchange.

There have also been reports that the trade volumes might have declined after Jaypee capital started limiting its exposure due to the Sebi probe.

In a separate matter, the Sebi board was also apprised on November 24 about the possible adverse effects of algorithmic trading strategies employed by market participants, the need for enhanced supervision and monitoring and that Sebi was actively working upon a policy to strengthen the risk mitigation measures.

"Further, the episode of one such algorithmic strategy going awry on a particular Exchange was explained to the Board," Sebi said, without naming this bourse as well.

As per reports, one case of rogue algo trade was reported by the BSE platform during the special muhurat (inaugural) trading session on the Diwali day last October. The exchange had anulled all derivatives trade for the day on October 26.