Two tennis umpires have been banned and four more are being investigated by the International Tennis Federation on charges of corruption.
The organisation has revealed it banned Kazakhstani Kirill Parfenov for life in February 2015 and suspended Croatia's Denis Pitner for a year last August.
Other umpires are under investigation for allegedly taking bribes to manipulate scores on the Futures Tour.
This follows BBC and BuzzFeed claims of match-fixing at tennis' top level.
That joint investigation uncovered files showing that, over the past 10 years, 16 high-ranking players have been repeatedly flagged to the Tennis Integrity Unit (TIU) over suspicions they have thrown matches.