Federal Bureau of Investigation agents raided Monday the offices of three hedge funds as part of a high-profile insider-trading investigation, and more could be on the way, according to people familiar with the matter.

The offices of Diamondback Capital Management LLC and Level Global Investors LP were raided. Both hedge funds are run by former managers of Steven Cohen's SAC Capital Advisors.

The third firm raided is Loch Capital Management LLC, based in Boston, people familiar with the matter said. Leonard Pierce, a lawyer for Loch Capital, declined to immediately comment.

"The FBI is executing court-authorized search warrants in an ongoing investigation," said Richard Kolko, an FBI spokesman. He declined to comment further.

Diamondback Capital Management said Monday that it was cooperating with the investigation.

"We received an inquiry this morning from the FBI," the hedge fund firm said in a statement provided to MarketWatch. "Diamondback is voluntarily cooperating. The firm is fully operational and we, along with our team, continue to manage the portfolio and Diamondback's business for the benefit of our investors," it added.

The move by the FBI follows an article by The Wall Street Journal describing an insider-trading investigation that is expected to encompass consultants, investment bankers, hedge-fund and mutual-fund traders. The investigation is said by people close to the situation to eclipse in size and magnitude past insider-trading probes.

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