The Justice Department on Wednesday opened a civil rights investigation into Fairfax County Commonwealth’s Attorney Steve Descano over allegations his office gave preferential treatment to illegal immigrants in criminal cases, intensifying scrutiny of one of Virginia’s most prominent progressive prosecutors.

In a letter sent Wednesday, Assistant Attorney General Harmeet Dhillon said the DOJ’s Civil Rights Division is examining whether Descano’s office violated federal law by considering “immigration consequences” when making charging decisions, plea agreements, and sentencing recommendations.