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President Donald Trump's longtime personal aide John McEntee has been fired and is under investigation by the Secret Service for serious financial crimes, according to two federal law enforcement officials.

McEntee's security clearance had been "in limbo for some time," one of the officials added.

Sources close to McEntee, a 27-year-old former football player for the University of Connecticut, said he struggled with a gambling addiction and they believe the investigation may be related.

One of those sources said McEntee's firing was abrupt and that he was asked to leave immediately on Monday after learning his security clearance had been revoked. One of the federal law enforcement officials who spoke to NBC said the FBI, which handles security clearance investigations, also has been collecting information on McEntee's gambling habbits.

His firing marks yet another departure in an executive office marked by a revolving door of hirings and firings and plagued by issues obtaining security clearances.