The Securities and Exchange Commission has instigated an inquiry into the operations of Thomson Financial's Capital Markets Intelligence Service.
The Canadian-based firm says it has received a subpoena from the US watchdog for documents relating to the operations of the divison.
In a statement, the company says: "Thomson Financial is co-operating fully with the SEC and has been informed that the inquiry should not be construed as an indication by the commission or its staff that any violation of law has occurred."
Thomson Financial's CMI business collects stock ownership data for public company clients who want to identify their institutional shareholder base. In 2003, the division contributed approximately $33 million to Thomson Financial's $1.5 billion in annual revenues.