Prosecutors from the U.S. attorney's office in the District have been busy recently probing whether executives at mortgage giant Fannie Mae profited from accounting irregularities, sources said, collecting hundreds of boxes of documents from regulators and participating in interviews of a whistle-blower.

The inquiry began in recent weeks after the Office of Federal Housing Enterprise Oversight released a report alleging widespread efforts by Fannie Mae executives to manipulate financial statements to meet Wall Street's earnings expectations. The report said that on at least one occasion executives manipulated earnings to trigger millions of dollars in bonuses for themselves. The inquiry is being coordinated with a parallel probe by the Securities and Exchange Commission.

The actions of federal prosecutors in the District appear to be a sharp contrast to the pace of a long-running criminal inquiry by the U.S. attorney's office in Alexandria, which opened an investigation last year into Fannie's smaller rival, McLean-based Freddie Mac. Freddie acknowledged then that it had understated its profit by nearly $5 billion over several years. The Virginia prosecutors have neither sought documents from the oversight office nor conducted interviews with current or former employees, according to sources familiar with the probe.

A spokesman for Paul J. McNulty, the chief federal prosecutor for the Eastern District of Virginia, declined to comment except to say that the investigation is ongoing.

SEC attorneys conducting a civil fraud investigation of Freddie Mac have been interviewing former company executives forced to resign last year in connection with accounting errors that resulted in the company's financial restatement. Lawyers for the Eastern District of Virginia have sat in on some SEC interviews but have not asked questions, said sources who spoke only on the condition their names not be used.

Some lawyers who have been following the case said the inactivity might indicate that McNulty is waiting for the SEC to conclude its probe before deciding whether to press criminal charges. That strategy is not unusual, they said. They point to the high hurdles the Virginia prosecutors would face in trying to make a criminal case. That includes trying to explain to a jury what is wrong with a company understating its earnings and trying to prove that executives intentionally falsified financial statements.

Justice Department investigators have been active in one area related to Freddie Mac in recent months. An FBI agent has asked former and current Freddie employees about the fundraising activities of the company's former chief lobbyist, R. Mitchell Delk, sources said.

Delk was ousted earlier this year after Freddie conducted an internal probe of his personal fundraising activities for prominent Republicans, including Rep. Michael G. Oxley (Ohio), chairman of the House Financial Services Committee, which oversees Freddie Mac's activities. Among the issues was whether Delk used Freddie Mac assets during his fundraising activities, which would violate company policy and possibly federal election law.

Freddie Mac referred the results of its Delk probe to the Federal Election Commission, which already was examining a complaint that Delk violated election law by getting a steep discount for fundraising dinners he sponsored at the pricey Galileo restaurant. Kenneth A. Gross, Delk's attorney, declined to comment.

The outcome of the election commission's probe will determine whether Delk's ouster will be considered a resignation or a firing for misconduct. If misconduct is found, Delk could lose at least $2 million in stock options he would otherwise be entitled to upon being terminated, according to sources familiar with the situation.

Paul J. McNulty, chief federal prosecutor for the Eastern District of Virginia, says the probe is ongoing.