Steven A. Cohen's SAC Capital Advisors LP got a government request for documents as the U.S. widens a probe of Wall Street insider trading that has implicated former traders at the firm.

The request came from U.S. officials, according to a person familiar with the matter.

The person, who declined to be identified because the situation is private, didn't disclose the scope of the request or what form it took.

Federal Bureau of Investigation agents, probing possible illegal trading by hedge funds, on Monday searched the offices of Level Global Investors LP and Diamondback Capital Management LLC. Both firms were founded by former SAC employees. Wellington Management Co., the Boston money manager that oversees $598 billion, also got a request for documents from U.S. investigators, according to a person familiar with the firm.

No allegation of wrongdoing has been made against SAC, of Stamford, Conn., which manages $12 billion. Jonathan Gasthalter, a spokesman for the firm, declined to comment.

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