The Department of Justice has opened a criminal investigation of accounting practices at Fannie Mae, the latest development in a brewing crisis for the mortgage giant. The criminal probe was confirmed Friday by an anonymous source. The accounting irregularities under suspicion are the alleged delay of reporting expenses to ensure company executives received bonuses.

Reviews by the Office of Federal Housing Enterprise Oversight, the government body charged with oversight of the lender and its counterpart Freddie Mac, first triggered suspicions last month. View the OFHEO report here [PDF]. The SEC has already begun an investigation of the firm. AP has more.