French Top 14 club Stade Francais said on Monday they had halted training and put their squad and coaching staff into isolation after recording positive coronavirus tests last week.
According to newspaper L'Equipe, 25 individuals from the Parisian outfit have contracted the virus after returning from a pre-season camp in Nice less than a month before the new campaign starts.
Gonzalo Quesada's side, who had the league's biggest budget last term thanks to billionaire owner Hans Peter-Wild, have cancelled a pre-season fixture with Brive and are scheduled to face Toulon on 27 August.
They open the new Top 14 term by hosting Bordeaux-Begles, who were top of the table when last season was declared over due to the pandemic, on 4 September.
"After carrying out Covid-19 tests this Monday August 10, it appears the health situation at Stade Francais has deteriorated despite respecting health and safety measures and advice from the regional health board," they said.
The players and personnel will remain in quarantine until 17 August before new examinations are carried out on their release.