BREAKING: Defense Sec Lloyd Austin was hospitalized due to prostate cancer: Walter Reed

The nation's most senior military official, was admitted to the Walter Reed National Military Medical Center on January 1 after suffering "complications following a recent elective medical procedure," but neglected to inform Biden of his absence until January 4.

According to CNBC, officials at the medical center confirmed on Tuesday that Austin, 70, had been admitted to undergo the original surgery on December 22, but developed a number of symptoms including nausea and severe pain six days later.

As a result, he was admitted to the intensive care unit and treated.

"Secretary Austin continues to recover well and remains in good spirits," a DoD spokesperson said, per the BBC. "He's in contact with his senior staff and has full access to required secure communications capabilities and continues to monitor DoD his day to day operations worldwide."

He has apologized for failing to ensure that "the public was appropriately informed."

In the days since news of Austin's hospitalization broke, Republicans in Congress have expressed significant outrage, claiming that the DoD "deliberately" withheld his medical condition in a "shocking defiance of the law."

Montana GOP congressman Matt Rosendale even went so far as to suggest Austin should be impeached, claiming he "violated his oath of office" on multiple occasions, and is thus "unfit for the Office of the Secretary of Defense."

Rosendale urged his colleagues to join him in "impeaching him to protect the American people."

As a result of Austin's actions, White House Chief of Staff Jeff Zients ordered Cabinet members and secretaries on Tuesday to notify his office immediately if anyone is unable to perform their duties.

“Agencies," he wrote in a memo, per the Toronto Star, "should ensure that delegations are issued when a Cabinet Member is traveling to areas with limited or no access to communication, undergoing hospitalization or a medical procedure requiring general anesthesia, or otherwise in a circumstance when he or she may be unreachable."

This is a breaking story and will be updated.