New details emerged Wednesday to indicate that Secretary of Defense Lloyd Austin’s chief of staff, Kelly Magsamen, was aware of her boss’ hospitalization on Tuesday last week but did not inform Deputy Defense Secretary Kathleen Hicks.

Pentagon press secretary Maj. Gen. Pat Ryder told reporters this delay was in part due to Magsamen having the flu.

A senior U.S. defense official told Fox News on Wednesday that a military assistant from Austin’s office notified a counterpart in Hicks’ office of the transfer of authority to her on Jan. 2.

Then on Thursday, Jan. 4, it was Magsamen who notified the chief of staff for Hicks that Austin had been hospitalized on Monday, Jan. 1, and that his condition was improving.

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When asked by Fox News if it was senior military assistant Lt. Gen. Ron Clark who spoke to the military assistant in Hicks’ office on Tuesday, the senior U.S. defense official did not have an answer and said a 30-day review will cover exactly who the military assistant was.

President Biden first learned of Austin’s prostate cancer on Tuesday, which was the same day as the public and a month after the diagnosis. This is despite the two speaking on the phone on Saturday.

Walter Reed National Military Medical Center revealed Tuesday that Austin was diagnosed with prostate cancer in early December and underwent a prostatectomy on Dec. 22.

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The hospital added that the 70-year-old recovered uneventfully from his surgery and was released the following morning. His prostate cancer was detected early and the prognosis was “excellent,” according to the facility.

During his hospitalization, Austin transferred authority to Hicks and did not inform the White House nor the reason behind the transfer. The Defense Department has for days said Austin was initially at Walter Reed for an “elective medical procedure,” not prostate surgery.

White House National Security Council spokesperson John Kirby said Tuesday that Biden was not informed of Austin’s hospitalization until last Thursday and only learned of the cancer diagnosis on Tuesday.

Asked whether Biden believed the time-lapse was acceptable, Kirby said it was “not optimal.”

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“For a situation like this to go as long as it did without the commander in chief knowing about it or the national security adviser knowing about it or, frankly, other leaders at the Department of Defense, that’s not the way this is supposed to happen. The president understands that,” Kirby said.  

Fox News’ Bradford Betz and the Associated Press contributed to this report.