Facebook Inc. is seeking to add directors, including at least one woman, who can add diversity to its all-male board, people with knowledge of the matter said.

Facebook has been working with executive-recruiting firm Spencer Stuart to identify prospective board members, said the people, who asked not to be identified because the search is private. The addition of any new directors probably won't be announced until after Menlo Park, California-based Facebook holds its initial public offering, one of the people said.

The world's largest social networking service has drawn scrutiny for the lack of independent directors and gender diversity on its board, even as most of its 901 million users are women. Chief Executive Officer Mark Zuckerberg will control 57.3 percent of the company's voting power after the IPO, regulatory filings show. Adding outside directors who haven't been closely affiliated with the company would help the board hold executives accountable, said Dennis Carey, vice chairman at Korn/Ferry International, an executive-search firm.