BOSTON (AP) — Democrats in Congress are accusing the Education Department of interfering with an investigation by the agency’s independent watchdog.

Five lawmakers sent a letter to Secretary Betsy DeVos on Tuesday saying her deputy pressured the department’s inspector general on Jan. 3 to drop an internal investigation.

After the inspector general said she would continue, she was told she was being replaced. That decision was reversed after it became public.

Department spokeswoman Liz Hill denied the allegations and said they are being made “purely for political gain.”

The investigation is examining DeVos’ decision to reinstate an accrediting agency shut down by the Obama administration.

In the letter, lawmakers including Virginia Rep. Bobby Scott and Washington Sen. Patty Murray demand answers from DeVos and say they are “increasingly concerned” by the department’s actions.