A day after former Secretary of the Interior Ryan Zinke left office, the Washington Post reported that the Justice Department is investigating whether he lied to the Interior Department’s inspector general investigators.

Before his departure, the scandal-plagued Zinke, who has faced at least 15 investigations during his time with the administration, had been the subject of inspector general probes related to his real estate dealings in his hometown of Whitefish, Montana, as well as a conflict related to a proposed casino project in Connecticut and other actions taken during his tenure. While it’s not known exactly which matter Zinke might have lied about, the Post reported Thursday that sources said the matter did not have to do with the Montana land deal, making it possible it had to do with the accusations by Mashantucket Pequot and Mohegan tribes that Zinke had killed their casino proposal because of “improper political influence.”

As the Post noted, the crime of making false statements can be difficult to prove, as investigators will have to show Zinke knew what he was saying was false. But others in President Trump’s orbit have pleaded guilty to making false statements, including Michael Flynn, Michael Cohen, and George Papadopoulos. But Zinke, who was not a part of Trump’s campaign and does not appear to be of much interest to the special counsel investigation, may prove less of an attractive target to investigators.

A spokesman for former interior secretary told the Post that Zinke had participated in two inspector general interviews about the casino issue in Connecticut and that he “to the best of his knowledge answered all questions truthfully.”

After growing pressure over his scandals, as well as the president’s reported displeasure over unrelated matters, Zinke announced in December he would resign. He left office on Wednesday.