Tennis investigators are examining whether a match at this year's Wimbledon was fixed after suspicious betting patterns were reported.
The Tennis Integrity Unit (TIU), which was set up in 2008 to detect any corruption, has not revealed which match it is investigating.
The TIU is already investigating a US Open first-round match between Vitalia Diatchenko and Timea Bacsinszky.
"Both are the subject of routine, confidential investigation," it said.
The TIU said it received 96 alerts from July to September, including the two alerts from Wimbledon and the US Open.
Alerts come from regulators and betting organisations, who can report matches if they notice suspicious betting patterns.
"It is important to appreciate that an alert on its own is not evidence of match-fixing," added the TIU.
It states that unusual gambling patterns can be explained by factors other than fixing, such as incorrect odds setting, player fitness, playing conditions and well-informed betting.