The U.S. Education Department said it is investigating Denver Public Schools for alleged discrimination after the district converted a girl’s restroom on the second floor of East High School into an all-gender restroom while leaving the other bathroom exclusively for male students.

The U.S. Department of Education said on Tuesday it is investigating the Denver schools system for allegedly discriminating against women and girls by converting a female bathroom to all-gender.

Denver Public Schools called the decision to investigate the conversion of a women’s restroom into an all-gender facility as potential discrimination “unprecedented.”