Documents apparently showing evidence of widespread suspected match-fixing in the world of professional tennis have been leaked to the BBC and Buzzfeed News.
According to the documents, over the last ten years, 16 players ranked in the top 50 in the world have repeatedly flagged to staff at the Tennis Integrity Unit (TIU) over suspicions they have thrown matches.
However, all players investigated by the TIU, including winners of Grand Slam titles, were permitted to continue competing.
The TIU was set up in 2008 after allegations about match fixing in a game between Nikolay Davydenko and Martin Vassall, and says it has a zero-tolerance approach to match fixing. Both players were cleared of violating any rules.
Chris Kermode, head of the Association of Tennis Professionals (ATP), rejected claims that reports of match-fixing within tennis have not been thoroughly investigated, but said that any new information brought to light by the BBC and Buzzfeed investigations will be further examined.
A number of tennis stars, including Roger Federer and Novak Djokovic, have dismissed the allegations that match-fixing affects the highest levels of the sport.
However, Djokovic has previously admitted that he was offered £110,000 to throw a match in Russia 10 years ago. The 20-year-old Serb refused the offer and decided not to attend the tournament.