The Trump administration is suing Harvard University, saying it has refused to provide admissions records that the Justice Department demanded to ensure the Ivy League school stopped using affirmative action in admissions.

In a lawsuit filed Friday in federal court in Massachusetts, the Justice Department said Harvard has “thwarted” efforts to investigate potential discrimination. It accused Harvard of refusing to comply with a federal investigation and asked a judge to order the university to turn over the records.

Harmeet Dhillon, who leads the department’s Civil Rights Division, said Harvard’s refusal is a red flag. “If Harvard has stopped discriminating, it should happily share the data necessary to prove it,” Dhillon said in a statement.

Harvard officials did not immediately comment.