The Australian Football League is investigating an alleged breach of training protocols by Australian Rules players and staff of Adelaide Crows.
Under AFL regulations, players are restricted to training in pairs to maintain social distancing.
"It appears this may not have happened for the entirety of a skills session," Crows boss Adam Kelly said.
An assistant coach and 16 players are currently training under quarantine at a resort in the Barossa Valley.
"Players were told to complete any training in accordance with current AFL training protocols, which include not training in more than pairs and at all times maintaining social distancing, while staying at the facility," added Cox.
"We are in the process of gathering the facts and liaising with the AFL."
Meanwhile, players in Australia's National Rugby League who do not wish to receive an advised flu jab can instead sign a waiver in order to play when the season starts on 28 May.
Players were asked to have the injection as part of biosecurity protocols, and although 97% of more than 800 players and staff did so, some declined.
Some have also rejected an initial waiver form, but it has now been revised and ratified by the Australian Rugby League Commission.
"The protocols allow for exemptions to vaccinations under compelling circumstances, including requiring players to sign a release.
"Until an NRL-approved release is acknowledged and signed by players, they will not be permitted to train," the league said in a statement.