Securities and Exchange Board of India initiated investigations into 154 cases related to stock market manipulations in the last fiscal, logging the highest number of probes started in a single year since 2005-06.
During 2011-12, 154 new cases were taken up by Sebi for probe, but it completed investigation in only 74 cases, according to the regulator's annual report.
This was the highest number of cases taken up by Sebi since 2005-06, when it had witnessed registration of 159 cases.
The regulator had completed probe in 81 cases during that period.
The 2011-12 fiscal saw a sharp rise in the number of cases taken up for investigation by Sebi compared to the previous fiscal when it took up 104 cases.
Sebi initiated probe into 71 cases in 2009-10.
In the past fiscal, about 47 per cent of the cases were related to market manipulation and price rigging, and 17 per cent related to insider trading.
Other cases pertain to irregularities in capital issues, takeover violations and other violations of securities laws.
"Since, several investigation cases involve multiple allegations of violations, water-tight classification under specific category becomes difficult," Sebi said.
After completion of investigation, Sebi initiated further penal action as per the recommendations made in the probe reports and as approved by the competent authority.
The action included issuing warning letters, initiating enquiry proceedings for registered intermediaries, also initiating adjudication proceedings for levy of monetary penalties.
Since 1992-93, the number of cases undertaken by Sebi for investigation has reached to 1,617, while the number of cases resolved stood at 1,420 during the period.