The investigation covers a period of years during which certain current and previous staff at Takara Printing used confidential information provided by its customers to give them an advantage trading stock.

The company prepares and prints financial statements for nearly 2,000 companies, including annual reports and reports of shareholder meetings.

At least three people are suspected of having used information on companies' takeover bids to buy stock in the target company ahead of formal announcements.

The investigation, which began last summer, found that one former staff had made multiple millions of yen from the practice while working at the company.

The original Daily Yomiuri Online story can be read here.