The Isle of Man is at the centre of a US Securities and Exchange Commission investigation into insider trading.
The probe centres on Myron Wentz, chairman and chief executive of personal care product and nutritional supplements distributor Usana Corporation.
In February, he sold 85,000 shares making more than £25 million.
Regulators are looking at Mr Wentz's web of offshore accounts that hold more than 8 million shares, a web which includes the Isle of Man.
Private investigators are going through corporate filings here looking at Mr Wentz's stock ownership structure.