Independent investigator Paul O'Sullivan was arrested on Monday, reported eNCA on Monday evening.
The station said that O'Sullivan's lawyer told eNCA that he was taken into custody in Centurion. No details of the charges were available.
On Friday, his home was reportedly raided, and his assistant detained.
O'Sullivan has been investigating acting national police commissioner Lieutenant General Khomotso Phahlane and had called in the Independent Police Investigative Directorate (IPID) to look into how Phahlane could afford his home which is believed to be worth about R8 million. That investigation has been the source of conflict between Phahlane and O'Sullivan.