BOSTON, March 14 (Reuters) - Fidelity Investments, the world's biggest mutual fund firm, said on Friday a U.S. Securities and Exchange Commission investigation of anti-money laundering practices at its funds and three-broker dealer units did not find any violations.

Fidelity spokeswoman Anne Crowley said the SEC is still examining one more broker-dealer unit -- Fidelity Brokerage Services. "We believe it's nearing completion as well," Crowley said. The examinations began in mid-2007, she said.

The Boston Business Journal said earlier on Friday the SEC and a federal grand jury are investigating Fidelity's anti-money laundering practices.

The SEC probe was launched after a former Fidelity employee, David van Duyn, sued the money manager for wrongful termination, the newspaper said.

Crowley said Fidelity is not aware of a grand jury investigation. "No one from the U.S. Justice Department has contacted us in this matter and we also have not received any subpoenas regarding this," she added.

The three broker-dealers where the SEC examinations were completed are Fidelity Distributors Corp, National Financial Services LLC and Fidelity Investments Institutional Services Co, Crowley said.

"In the (SEC) letters, they told us they had completed the examination and identified no violations of the rules and also said there were no deficiencies that came to their attention during the course of the examination," the spokeswoman said.

Fidelity had about $1.5 trillion in assets under management as of end January. (Reporting by Muralikumar Anantharaman; Editing by Tim Dobbyn)