“Cologne will not confirm any names out of respect for the privacy of those affected.”
The club said it would continue to train in preparation for the campaign to resume, with further tests to be carried out as part of the league’s health and safety protocol.
“We now see in everyday life that our concept recognises and reduces risks at an early stage,” said Tim Meyer, head of the German league’s medical task force.
“We are convinced that with our concept, we can enable players to practice their profession with the best possible protection against infection.”
The Bundesliga had set a target return date of May 9 but still needs permission from the German government.
A delay on the decision this week meant a resumption would not be possible before May 16.
A final decision is expected next Wednesday.
The German league confirmed Thursday that clubs had started testing players for the virus as part of plans to get the season up and running again.
It has been suspended since March 13.
‘Will go down’
Clubs returned to training at the start of April while adhering to social distancing guidelines and games would be played behind closed doors, with large-scale public events banned in Germany until August 31.
Borussia Dortmund chief executive Hans-Joachim Watzke warned last weekend that “the entire Bundesliga will go down” unless the league restarts.
Germany’s top clubs are desperate for the season to be completed by June 30 in order to claim an instalment of television money worth 300 million euros ($325 million).
A return in May would make the Bundesliga the first top league in Europe to resume as Germany cautiously eases lockdown measures.
Nevertheless, there is heated debate about whether the Bundesliga should resume amid the pandemic which has so far claimed the lives of more than 6,000 people in Germany.
Paris Saint-Germain were declared Ligue 1 champions on Thursday after French Prime Minister Edouard Philippe announced sport could not resume in France before September.
Meanwhile, English Premier League clubs on Friday reconfirmed their commitment to finish the season subject to coronavirus restrictions being lifted.
There are still 92 games remaining. They will be behind closed doors with neutral venues suggested.
Italy’s 20 Serie A clubs on Friday also reiterated their unanimous desire to complete the season despite sports minister Vincenzo Spadafora this week saying the chances of restarting were “increasingly narrow”.
In Spain, La Liga is planning to start testing players for the coronavirus between Tuesday and Thursday next week, after which they would then be able to resume individual training programmes within 48 hours.
“I hope that we can start playing in June. We have until June 28,” league president Javier Tebas said.