Scotland's government has warned that it could halt the new Premiership soccer season after Celtic's Belgian defender Boli Bolingoli broke quarantine rules.
Bolingoli, 25, played in Celtic's 1-1 draw at Kilmarnock on Sunday without quarantining after returning from Spain - where he had travelled without informing the club.
He apologised, saying he was guilty of an error in judgement, while Celtic promised an investigation.
"We are currently in discussion with the club and football governing bodies to establish the facts," the Scottish government said in a statement on Tuesday.
"If confirmed as another serious incident within Scottish football, where protocols have been breached at the risk of wider public health, then the Scottish government will have little choice but to consider whether a pause is now needed in the resumption of the game in Scotland."
Celtic said they had apologised to all clubs in the league.
Steven Gerrard, the manager of Celtic's local rivals Rangers, said the government's warning should serve as a wake-up call.
"If mistakes continue to happen, there's no doubt the season will be cancelled," he was quoted as saying by Sky Sports.
Aberdeen's Premiership match against St Johnstone was postponed on Friday after two of their players tested positive for COVID-19, with six others self-isolating.