The Justice Department has opened a criminal probe into reports that the Internal Revenue Service gave special and unwarranted scrutiny to tax-exempt applications made by conservative groups. According to a Treasury Inspector General report, the practice began in early 2010. The groups in question had applied for tax exempt status as 501C-4s. These types of organizations can be set up to pursue primarily social welfare objectives, but they're allowed to engage in some political activity. The agency has apologized for the incidents and says it’s taken corrective action, but more changes will probably be required.