Investors in Diamondback Capital Management, one of four hedge funds raided by federal authorities last year as part of an insider trading probe, have asked to pull more than $1 billion from the firm, a source familiar with the fund's communications to clients said on Tuesday.

The sum is up from the $722 million in redemption requests that Diamondback had reported on Friday.

Diamondback has more than $5.5 billion of capital.

Founders of Diamondback previously worked at SAC Capital Advisors, the firm overseen by Steven Cohen. Its clients have included public pension funds in Indiana, Missouri, New Mexico, New York and Philadelphia, Pennsylvania.

Diamondback has not been implicated in the insider trading probe. The firm did not answer a call after market hours seeking comment.

The New York Times originally reported the increase in redemption requests earlier on Tuesday.

(Reporting by Svea Herbst-Bayliss and Jonathan Stempel; Editing by Gary Hill, Bernard Orr)