NASD is examining whether some of the biggest brokerage firms inappropriately sold hedge fund products to individual investors, according to Bloomberg.

Officials at NASD's Washington headquarters refused to comment on letters sent as part of the investigation. However, Bloomberg reported that three people with direct knowledge of the probe said that the regulator has sent letters to Merrill Lynch, Citigroup and UBS, broadening the scope of an investigation that started in June.

Subscribe Now

Access to premium content including in-depth coverage of mutual funds, hedge funds, 401(K)s, 529 plans, and more.

3-Week Free Trial

Insight and analysis into the management, marketing, operations and technology of the asset management industry.