(Bloomberg News) Diamondback Capital Management LLC, among the hedge funds the FBI raided in November as part of an insider-trading probe, said it received withdrawal requests of about $534 million for the end of March.

The investor redemptions total about 9.4% of the firm's assets, Diamondback co-founders Rich Schimel and Lawrence Sapanski said in a Feb. 1 letter. Blackstone Group LP, which invests client money with Diamondback and had the most eligible for redemption without penalty, plans to keep most or all of the assets in the fund, said two people briefed on the matter who asked not to be named because the information is private.

Of the assets Diamondback oversees, 64% was eligible for withdrawal without penalty by the end of March, while 10% could be redeemed after paying a fee, according to the letter. About 19% of the firm's assets couldn't be withdrawn in the period. Diamondback, based in Stamford, Conn., said "several large" investors have stated their intention is to remain in the fund.

Blackstone has about $35 billion invested in hedge funds on behalf of clients. Spokesmen for Diamondback and New York-based Blackstone declined to comment.

Clients have until Feb. 15 to submit withdrawal requests for the current quarter.

November Raid

Diamondback had said the November raid by the Federal Bureau of Investigation was focused on one of its portfolio managers, who was put on leave. The firm said it was told by the government that it's not the target of the investigation. Hedge funds Level Global Investors LP and Loch Capital Management also had their offices raided by U.S. officials on Nov. 22.

Separately, Noah Freeman and Donald Longueuil, former employees of SAC Capital Advisors LP, according to a person familiar with the matter, were charged today as part of a nationwide investigation of insider trading at hedge funds, technology companies and so-called expert networking firms.

Federal prosecutors in Manhattan also charged Samir Barai, the founder of Barai Capital Management LP, who surrendered to authorities this morning, and Jason Pflaum, who worked for Barai and pleaded guilty yesterday as part of a cooperation deal.

The U.S. brought insider-trading charges against more than 30 people since the October 2009 arrest of Raj Rajaratnam, founder of the Galleon Group hedge fund.