WASHINGTON (Reuters) – The Federal Aviation Administration has reassigned three managers in its office overseeing Southwest Airlines Co, a person briefed on the matter said on Tuesday.

The FAA said in a statement that it takes “allegations regarding safety oversight and retaliation seriously …. To uphold these principles, we take appropriate action as necessary. We do not comment on personnel matters.”

The Wall Street Journal, which reported the FAA reassignments earlier on Tuesday, said they were “also prompted by allegations that managers retaliated against whistleblowers,” citing sources familiar with the matter.

The shakeup comes as the Transportation Department’s inspector general is auditing a number of issues related to the FAA’s oversight of Southwest.

The inspector general’s office said last year it was opening a review after “recent events have raised concerns about FAA’s safety oversight, particularly for Southwest Airlines” including a midair incident in April 2018 in which an engine exploded and one person was killed.

The inspector general said in June 2018 had received a complaint “regarding a number of operational issues at Southwest Airlines, such as alleged pilot training deficiencies, which raise concerns about FAA’s oversight of the carrier.”

In May 2018, the FAA said federal investigators were assigned to monitor Southwest maintenance operations, after whistleblower complaints of mistreatment of mechanics raised concerns. The agency said it found no rule violations and that the assignment of additional inspectors was standard practice to preclude any deterioration in maintenance.