A first-round match at the US Open is under investigation after suspicious betting patterns were detected.
The Tennis Integrity Unit (TIU) said it was looking into Timea Bacsinszky's win over Vitalia Diatchenko.
Swiss Bacsinszky, the 15th seed, beat Russia's world number 87 6-1 6-1.
The TIU said the alert did not mean match-fixing had taken place, adding: "There are many reasons other than corrupt activity that can explain unusual betting patterns."
It cited "incorrect odds-setting, well-informed betting, player fitness, fatigue and form, playing conditions and personal circumstances" as factors which could prompt betting organisations to raise an alert.
However, the organisation was critical of the manner in which details of the investigation were released, blaming a "leak".
"Publicising match alerts is premature and inevitably draws unwarranted attention to the players involved in the match," it said.
"Under the Tennis Anti-Corruption Program, all players are considered innocent unless proven otherwise at an independent anti-corruption hearing."