The investigation is in its earliest stages and is being conducted by the U.S. attorney’s office in Brooklyn, which has a long history of investigating the N.B.A. and professional sports, according to two of the people.
The authorities began scrutinizing the matter before the N.B.A. leveled a series of severe punishments last week against the Clippers, its owner and two top executives after a law firm working for the N.B.A. and its commissioner, Adam Silver, concluded that the team had engaged in a wide-ranging effort to break its rules.
The inquiry’s scope, targets and the possible crimes being examined were unclear. But prosecutors have issued at least one subpoena as part of the investigation, according to the two people.
Among the matters likely under scrutiny are a series of secret endorsement deals that Mr. Leonard signed, and whether Steve Ballmer, the team’s owner, and other executives helped facilitate them as a way of compensating him at a level that exceeded the N.B.A.’s salary cap.