Boca Juniors has announced that 18 of its players have tested positive for the coronavirus, just two weeks before restarting their Copa Libertadores campaign.
On Monday the Argentine giants suspended training for 72 hours after detecting what it said was an "outbreak" of Covid-19 at the club's training centre outside Buenos Aires.
New tests carried out on Wednesday confirmed 18 players had tested positive, but the Xeneize declined to identify them.
In a statement the club described eight of the cases as asymptomatic and the other 10 as mild.
Boca are due to play Paraguay's Libertad in Asunción when South America's Copa Libertadores resumes on September 17.
President Alberto Fernández cast doubt over the fixture in an interview with TN Television.
"It is very difficult to play in this context. Look at what is happening at Boca. Football is a contact sport," Fernández said.
Boca's Buenos Aires rivals River Plate have to visit São Paulo in the same competition.
"We have to look very carefully at the issue. It is not so simple, it is a pandemic. We are going to play in Brazil, which is in a very complicated situation. The epicentre of the pandemic is Latin America," said Fernández.
Argentina is one of the worst hit countries from the coronavirus pandemic in South America, with more than 400,000 infections and more than 9,000 deaths.
Boca were staying at the Ezeiza Sports Center, observing a special set of protocols as part of a so-called "health bubble" with no contact with the outside world.
"All of them will continue under strict sanitary isolation rules as indicated by the protocols," the club said.
The players will be tested again "prior to their reintegration to training," it said.