John Mack, chief executive of Morgan Stanley, will be interviewed by the Securities and Exchange Commission in an investigation of a hedge fund he participated in prior to taking over the Wall Street firm, the company said Friday.

The SEC has been looking into whether Pequot Capital Management Inc. acted on insider information in 2001 when trading shares potentially involved in an upcoming merger. A former SEC staff attorney testified before Congress last month that Mack was believed to be the tipster, which Mack has denied.