WASHINGTON — The Pentagon’s investigative arm has started to examine the matter involving Ronny L. Jackson, the Navy rear admiral whose nomination to lead the Department of Veterans Affairs collapsed last week amid allegations he mistreated White House medical staffers and improperly dispensed medications, among other accusations.

Tom Crosson, a Defense Department spokesman, said Monday that the Pentagon’s inspector general has received the allegations and is looking into the issue further to see if a formal probe is necessary. The office, he added, “is assessing what investigations and reviews have already been conducted related to these issues, any jurisdictional issues that may relate to the allegations, and the scope of the allegations and complaints related to these issues.”

From there, “The Inspector General’s office will determine what investigations or actions are warranted regarding these allegations and complaints,” Crosson said.

Jackson, who has served as White House physician under three administrations, has vehemently denied wrongdoing. A White House official said Sunday that he would remain with the medical unit there but that he would not return to his role as Trump’s physician. A White House spokesman later seemed to walk that back.

“Rear Admiral Ronny Jackson is currently on active duty, assigned to the White House as deputy assistant to the president,” White House principal deputy press secretary Raj Shah said Monday. “Despite published reports, there are no personnel announcements at this time.”

Jackson withdrew his nomination to lead VA last week under a firestorm that erupted when Sen. Jon Tester of Montana, the ranking Democrat on the Senate Committee on Veterans’ Affairs, disclosed the wide-ranging allegations Jackson’s colleagues brought to the panel. Tester’s staff has not provided documentation substantiating the most explosive allegations, including the claim that Jackson wrecked a government vehicle while intoxicated, though the senator’s aides have said that at least two people backed up each of the accusations.

White House officials have released some documentation in a bid to disprove parts of the allegations. For instance, a review of vehicle records yielded just three minor incidents involving Jackson. None corroborated allegations Jackson was involved in a drunken crash, according to the White House.

Trump has called on Tester, who is up for reelection this year in a state the president won by more than 20 points in 2016, to resign over his role in sinking Jackson’s VA nomination.

Jackson remains under scrutiny because he is up for a military promotion from one-star to two-star admiral. That nomination remains pending before the Senate Armed Services Committee, although Democrats on the panel have warned that the allegations must be reviewed first.

A spokeswoman for the committee did not return a request seeking clarity on the status of Jackson’s promotion.