The Tennis Integrity Unit (TIU) is investigating the first-round encounter between Alexandr Dolgopolov and Thiago Monteiro in Winston-Salem.
Dolgopolov fell, 6-3, 6-3, to an opponent ranked more than 40 spots below him.
While Monteiro was an underdog with bookmakers going in, the odds shifted just before the match began, making the Brazilian an apparent favorite. That indicates there was a large volume of betting on the lower-ranked player to win, and led some betting companies to suspend wagering on the match.
The TIU "was made aware of concerns" around the betting patterns, it said in a statement.
"As with all match alerts, the TIU will assess, make a judgement and take appropriate action on the information received," the unit said.
While unusual betting patterns can be an indication of potential match-fixing, they can also be triggered for other reasons, including knowledge of player injury.
The TIU did not suggest that it had received any indication that either player was implicated.
