State Department investigators reportedly interviewed hundreds of diplomats and employees at the U.S. embassy in Ukraine this week, as part of a probe into the alleged surveillance of former Ambassador Marie Yovanovitch. BuzzFeed News reports the Diplomatic Security Service, the State Department’s federal law enforcement and security arm, interviewed the employees on Wednesday and Thursday. The officials were also reportedly coordinating with a Ukrainian investigation into the alleged Yovanovitch surveillance, which was opened on Jan. 16. One source said the interviews seemed like a “cover your ass” move for Secretary of State Mike Pompeo, who has been criticized for his slow reaction to the surveillance news and who will visit Ukraine on Jan. 30 and 31. Almost a week before the DSS officers conducted interviews, Pompeo told news outlets he planned on investigating the alleged surveillance effort—which involved associates of President Trump’s personal attorney Rudy Giuliani. The embassy has not spoken publicly on the matter. This also comes after Pompeo berated an NPR reporter for asking questions about Yovanovitch and Ukraine in an interview.