The Department of Justice announced Wednesday that has opened an investigation into convicted sex offender and billionaire Jeffrey Epstein’s controversial plea deal.

The DOJ’s Office of Personal Responsibility is conducting the probe, which came in response to multiple letters from Sen. Ben Sasse (R-NE) following a bombshell Miami Herald report that detailed how Epstein—who has been accused of molesting more than 100 underage girls in Palm Beach, Florida—was granted a sweetheart plea deal in 2008 by now Secretary of Labor Alex Acosta and other DOJ attorneys.

“OPR has now opened an investigation into allegations that Department attorneys may have committed professional misconduct in the manner in which the Epstein criminal matter was resolved,’’ Assistant Attorney General Stephen E. Boyd wrote in his Wednesday letter to Sasse.