Germany's football league insisted on Monday the testing of players and backroom staff was "providing protection" despite 10 cases of coronavirus across the top two divisions as clubs prepare for a possible return to action this month.
The DFL reported that out of 1 724 tests, 10 had returned a positive result, three of which are already known to involve Bundesliga side Cologne.
"The tests carried out over the past few days have fulfilled their purpose of providing additional safety and thus protecting players as best as possible from infection during team training or matches," the DFL said in a statement.
The positive results all came from the first batch of tests as the German league prepares to resume from 16 May in empty stadiums and with strict hygiene measures.
The league's plans to become the first major European football competition to restart since the season was halted in mid-March include regular testing of players.
The DFL did not specify which clubs were involved, but three of the cases are already known to have been for two players and a physiotherapist at Cologne.
The league said those concerned have immediately been quarantined and the local health authorities informed.
The news of the positive tests is unfortunate timing given that the league is hoping to get the green light to resume from Chancellor Angela Merkel's federal government on Wednesday.
According to the regulations in force in Germany, anyone who has been in contact with a positive case must observe a 14-day isolation period.
On Sunday, Horst Seehofer, Germany's interior minister who has responsibility for sport, said he supported a resumption of the Bundesliga.
However, on Monday Seehofer's interior ministry said German football would not be allowed to deviate from the rules for the wider population.
"Horst Seehofer stands by what he said - anyone who has been in direct contact with a person who has tested positive must be quarantined for 14 days," said ministry spokesperson Steve Alter.
"This is a principle that applies to the whole population and there is no reason why it should be any different for professional footballers."
However, the league's plan to resume states that clubs would be able to continue training even if a squad member or coach tested positive for the coronavirus and was immediately quarantined.
Germany's top clubs are desperate for the season to be completed by 30 June in order to claim a €300 million instalment of money due from its television contract.
Merkel and the heads of the 16 federal states are due to give a decision on whether the league can resume in a conference call on Wednesday.