There were no positive results from Cologne's second round of coronavirus testing, the Bundesliga club announced on Monday.
Cologne revealed on Friday three unspecified individuals at the club had contracted COVID-19 and were told to undergo a 14-day quarantine procedure.
Further testing carried out on Sunday found no further cases of coronavirus.
A statement from Cologne read: "On Sunday, 1. FC Koln had the entire team, as well as the coaching and backroom staff, tested for COVID-19. All tests from the independent laboratory were negative.
"On Monday morning, Markus Gisdol's team will continue to train in groups. Training is not open to the public.
"The medical concept from the DFL [German Football League] sees the regular testing as a prerequisite for the possible continuation of the league.
"Only players who have been tested negatively twice in succession are allowed to train and play."
Cologne midfielder Birger Verstraete criticised the decision to continue training in the aftermath of the positive tests, though he later backtracked on his comments.
The Bundesliga has been suspended since March 13 due to the coronavirus pandemic but a decision on its potential resumption will be made on Wednesday.
Cologne have stated they are ready to move into a "quarantine-like" training camp if the green light is given to finish the 2019-20 season behind closed doors.