Three matches at this year's Wimbledon tournament triggered alerts for possible match-fixing, the Tennis Integrity Unit (TIU) has revealed.
One of the matches was from the main draw and the other two were in the qualifying rounds.
They will be assessed and reviewed by the TIU as part of its latest quarterly review, alongside one match from the French Open.
Alerts are raised in response to unusual betting patterns, which are not in and of themselves evidence of match-fixing. Several other factors, such as playing conditions or an injury to one of the players, could account for anomalous betting patterns.
The TIU receives information about suspicions of match-fixing from betting companies and regulators, and is obliged to investigate should a red flag be raised.
The suspicious matches at Wimbledon are not believed to be related to the unusually high 10 mid-match retirements in this year's men's tournament. It is also understood that no British players are under investigation.
The matches at Grand Slam level that prompted alerts are the biggest cause for concern, but as usual, unusual betting patterns are most rife in the lower levels of the game.
The majority of alerts (40 out of 53) were received for matches played on the lower level men's ATP Challenger and ITF Futures circuits. Fitting into this pattern was the 28-year-old Australian Isaac Frost, who has never been ranked higher than 651, being charged with match fixing last month.
In total, during the period in question, 31,281 professional matches were played, with the 53 alerts featuring in just 0.169% of those matches.
Looking at this year as a whole, the cumulative six-month match alert figure for 2017 is now 83, which is comfortably down on the 121 received for the same period in 2016.
The next wave of the TIU's quarterly figures will be published in early October.
The TIU did not specify which matches were under investigation, but probaby the most obvious case of a player potentially "tanking" during Wimbledon was Aussie Bernard Tomic, who lost in straight sets to German Mischa Zverev in the opening round.
Tomic admitted to being "bored" and calling an unneeded medical break. He was fined $US 19,725 ($NZ26,820) - the second largest penalty in Wimbledon history - and dropped by his Head racquet sponsor.
Often, though, match-fixing in sport is not that obvious and may not be a case of losing a match, but simply influencing isolated events along the way, like no-balls in cricket or perhaps double-faults in tennis.