A top aide to US Defense Secretary Pete Hegseth, Dan Caldwell, was removed from the Pentagon earlier this week amid an active investigation into suspected leaks of sensitive defense information, according to a US official who spoke with Reuters on Tuesday. Caldwell has been placed on administrative leave following what the source described as “an unauthorized disclosure.” The specific nature of the information allegedly leaked remains unclear, and officials have not revealed whether the disclosure was made to a journalist or another party. “The investigation remains ongoing,” the official told Reuters , declining to offer further details. The probe stems from a memorandum dated March 21 and signed by Hegseth’s chief of staff, Joe Kasper, which called for an inquiry into “recent unauthorized disclosures of national security information involving sensitive communications.” The memo also indicated the potential use of polygraph testing, although it is not known whether Caldwell underwent such a procedure. While not as publicly visible as other senior officials at the Department of Defense, Caldwell has been regarded as an influential adviser to Secretary Hegseth, according to Reuters . Related articles: Second US aircraft carrier joins operations against Houthis US troops may have contracted COVID months before outbreak Pentagon investigating Pete Hegseth's role in 'Signalgate' US deploys B-2 bombers and carrier strike groups His significance within the administration became more apparent following the publication of leaked Signal messages reported by The Atlantic last month. In those communications, Hegseth identified Caldwell as the ideal liaison for the National Security Council in connection to military operations targeting Houthi forces in Yemen. Despite the gravity of the current situation, no formal charges have been announced, and the Department of Defense has yet to make an official statement on Caldwell’s status.