The office is involved in investigations at Apple Computer and dozens of other companies. In some cases, the Securities and Exchange Commission is considering moving ahead with civil cases, instead of waiting for the U.S. Justice Department, the Financial Times reported.
Kevin Ryan was one of eight U.S. attorneys fired by the Bush administration. Chris Steskal, who headed the options task force, has also left.
Scott Schools, who serves as temporary U.S. attorney, stayed on instead of leaving last week so someone would be in charge.
Michael Wang, who heads the office's criminal division, told the newspaper he does not believe the departures have caused major problems.
"Some degree of turnover is a fact of life," he said. "We have a robust inventory of white-collar cases here, and there remain extraordinary attorneys in this office who are more than capable of handling each and every one of them."