The Defense Department’s (DOD) deputy chief of staff was placed on administrative leave on Tuesday, following the steps of another Pentagon official earlier in the day.Darin Selnick, the deputy chief of staff for Defense Secretary Pete Hegseth, has been removed, a senior U.S. official confirmed to Fox News.Selnick is under investigation for the same leak probe that saw Hegseth aide Dan Caldwell escorted out of the Pentagon by security. Both Selnick and Caldwell are on administrative leave.According to the Pentagon’s website, Selnick is a retired Air Force officer who has worked extensively in veterans’ affairs organizations.”Mr. Selnick leverages his extensive government and non-government experience advocating for veterans to position Service members for productive post-separation lives from the first day they put on a uniform,” the biography states.GENERAL WHO HELPED TRUMP DECIMATE ISIS TERRORISTS IN FIRST TERM CONFIRMED AS JOINT CHIEFS CHAIRMANBoth Selnick and Caldwell worked for Concerned Veterans for America in the past, a group formerly led by Defense Secretary Pete Hegseth.Reuters reported that Caldwell was placed on leave for an “unauthorized disclosure,” as part of an investigation into leaked Pentagon documents.The probe was announced last month, and concerned itself over “recent unauthorized disclosures of national security information.” HEGSETH QUIPS ‘99.9%’ OF DEI INITIATIVES ARE GONE FROM THE MILITARY UNDER TRUMP’S WATCH”The use of polygraphs in the execution of this investigation will be in accordance with applicable law and policy,” DOD Chief of Staff Joe Kasper wrote in a memo at the time. “This investigation will commence immediately and culminate in a report to the Secretary of Defense.”An official told Politico that the leak concerned Panama Canal plans and Elon Musk’s visit to the Pentagon, among other matters.More information about the leak is unknown, and there is currently no evidence to connect Caldwell or Selnick to that leak.Fox News Digital’s Morgan Phillips contributed to this report.