ST. PAUL, Minn. (AP) — The Minnesota Department of Health is requiring nearly 600 nursing assistants to retake their registration exams.

The Star Tribune reports that follows an investigation that found "potential improprieties" at two Inver Hills Community College sites.

The Health Department announced the move Tuesday. It follows an investigation into a "suspicious pattern in test results" at Inver Hills' Center for Professional and Workforce Development, and its satellite location at Blue Sky Online in West St. Paul. Minnesota State Colleges and Universities joined in the announcement.

The requirement affects all students who took tests at the two sites between May 1, 2014, and Oct. 16, 2015, to become federally qualified nursing assistants — regardless of whether their specific test results were questionable.

Nursing assistants monitor patients at nursing homes and care facilities.