Strasbourg have confirmed four new positive coronavirus cases within the "professional organisation" with the new Ligue 1 campaign under three weeks away.
The French side confirmed five people at the club had contracted the virus on July 29, announcing the new detections on Tuesday following tests a day earlier.
"These tests unfortunately confirm what we feared but we are working in close collaboration and in total transparency with the Regional Health Agency (ARS)," said team doctor Francois Pietra.
"A specific preventive health protocol is implemented by the club and we apply all the instructions recommended by the authorities."
Strasbourg said those affected were placed into isolation and told to quarantine.
The club have consequently cancelled a friendly against Reims on Saturday, while their top-flight campaign is scheduled to start with a trip to Lorient on August 23.
Strasbourg finished 10th last season in Ligue 1, a campaign that was ended in March with most teams still left with 10 games to play and decided on a points-per-game basis due to the outbreak of COVID-19.
