WASHINGTON — Three former senior advisers to Defense Secretary Pete Hegseth decried on Saturday what they called “baseless attacks” after each was escorted from the Pentagon in an expanding probe on information leaks.

Dan Caldwell, a Hegseth aide; Colin Carroll, chief of staff to Deputy Defense Secretary Stephen Feinberg; and Darin Selnick, Hegseth’s deputy chief of staff were among four officials in Hegseth’s inner circle who were ousted this past week.

While the three initially had been placed on leave pending the investigation, a joint statement shared by Caldwell on X said the three were “incredibly disappointed by the manner in which our service at the Department of Defense ended. Unnamed Pentagon officials have slandered our character with baseless attacks on our way out the door.”

“At this time, we still have not been told what exactly we were investigated for, if there is still an active investigation, or if there was even a real investigation of ‘leaks’ to begin with,” the post said.

Former Pentagon spokesman John Ullyot also announced he was resigning this week. The Pentagon said, however, that Ullyot was asked to resign.

The upheaval comes less than 100 days into the Trump administration where the Pentagon has found itself frequently in the epicenter of controversial moves — from firings of senior military and civilian staff to broad edicts to purge content that promoted diversity, equity or inclusion. That led to images or other online content of heroes like the Tuskegee Airmen and Jackie Robinson being temporarily removed from the military’s websites, causing public uproar.

Last month, Hegseth announced that the Pentagon’s intelligence and law enforcement arms were investigating what it says are leaks of national security information following reports that Elon Musk was set to receive a classified briefing on potential war plans with China.

In the announcement by Hegseth’s chief of staff, Joe Kasper, the office warned that Defense Department personnel could face polygraphs in the probe.

The departures also follow the firings of senior military officers, including Joint Chiefs Chairman Gen. CQ Brown; Chief of Naval Operations Lisa Franchetti; National Security Agency and U.S. Cyber Command director Gen. Tim Haugh; and Vice Adm. Shoshana Chatfield, the U.S. military representative to the NATO Military Committee.