The financial watchdog expressed concerns that information relating to certain mergers and acquisitions deals had been leaked.
According to the FSA's Market Watch newsletter, the investigation will involve "looking at a small number of deals where there was a leak of information", although details of the specific deals and the companies involved have not been released.
All parties involved, including associated law firms and advisors, would be investigated, the FSA added.
"In this review, we will meet specific 'deal teams' to go through the chronology of deals, undertaking a high-level study of IT systems and security and reviewing hard-copy filing systems, together with a sample review of documents," it said.
British newspapers including the Financial Times and the Guardian report that four takeover bids from the last 12 months are being specifically looked at.
