The Windsor-Essex County Health Unit is asking anyone who attended a basketball tournament in Oshawa earlier this month to get a COVID-19 test "as soon as possible" following an outbreak.
On Monday, the Durham Region Health Department said more than 20 attendees have tested positive for the disease so far.
About 7,000 people are believed to have attended The Jane and Finch Classic basketball tournament, held over five days from Aug. 3 to 8, at the Playground Global facility in Oshawa.
In a statement, Windsor-Essex's medical officer of health Dr. Wajid Ahmed said people should get tested as soon as possible as there's been cases in a number of teams and athletes across "multiple jurisdictions."
The statement did not say whether any cases have been confirmed in Windsor-Essex.
In a statement from Durham Region Health, the department also made a public appeal for attendees to get tested, saying they were "having difficulty reaching all players and spectators" as they were "from all over Ontario and other provinces."
Cases from Quebec, Peel, Toronto, and Durham have so far been identified.