PJ City FC confirmed that six players and three coaches had tested positive for Covid-19 two weeks ago.
The Super League side disclosed that all, except one, have since recovered.
PJ City chief executive officer S. Ganesh confirmed the cases yesterday.
"We had a few players who tested positive at the end of December.
"We are unsure of how they contracted Covid-19. As of now, we still cannot identify the source of it.
"One player is still observing self-quarantine while the rest have been cleared after the second test.
"We have informed the Malaysian Football League (MFL) and the other concerned parties. However, we cannot reveal the identities of those who had Covid-19.
"We are all good now. The team are planning to play some friendly matches," said Ganesh.
The MFL should take additional measures ahead of the new M-League season next month to ensure the safety of players, coaches and officials.
Meanwhile, MFL chief executive office Datuk Ab Ghani Hassan confirmed that PJ City had informed them about the Covid-19 cases.
"The club did so on Dec 25 after one of their coaches tested positive.
"The team members were tested on Dec 29, and a few of them were positive. They were warded. Except for one player, the others have recovered," said Ghani.
Ghani confirmed that the players and coaches did not contract the virus during training.
"I hope teams will follow the standard operating procedures (SOPs) during training and friendly matches.
Last year, five Kuching FA players tested positive for Covid-19 but have since recovered.