A company spokesman said the Securities and Exchange Commission, the US financial watchdog, was investigating whether an Oechsle portfolio manager had attempted to manipulate the price of a London stock via the investment banks Morgan Stanley and ABN Amro.
Oechsle declined to name the fund manager involved, who has been placed on administrative leave, but sources close to the investigation suggested it was Andrew Parlin, an employee of the company since 1988.
Morgan Stanley and ABN Amro were fined a total of pounds 350,000 earlier this week for accepting instructions from a previously unnamed US customer to move a share price on the London Stock Exchange.
The Exchange has declined either to provide details of the dealings or to identify the affected stock. An Exchange spokesman refused yesterday to comment on reports that named the stock as British Biotech.