Celtic are launching an investigation after it emerged their defender Boli Bolingoli took a secret trip to Spain and failed to self-isolate on his return.
The Belgian player later came off the bench in Celtic’s Scottish Premiership game against Kilmarnock on Sunday.
The Scottish government added Spain to the list of countries where returning travellers had to quarantine for 14 days following a decision that came into force on 26 July.
In a statement, Celtic said a “full investigation will now take place and the club will take all appropriate action”.
It added: “Celtic Football Club has taken its response to COVID-19 extremely seriously and we are pleased that, to date, we have recorded no positive tests.
“Our staff have given so much in this area, working tirelessly to ensure that all players and other club personnel are safe, fully aware of their own responsibilities and familiar with all guidance and protocols. Safety must always be our priority.”
The news is more unwelcome attention for Scottish football.
Aberdeen’s game against St Johnstone on Saturday was postponed for 24 hours as two Aberdeen players tested positive for COVID-19 and a further six were instructed to self-isolate after a night out in a bar.
Scottish government officials held a meeting with the league’s managers and captains on Monday where they were reminded of their responsibilities over protocols particular to football and also to the public.
First Minister Nicola Sturgeon warned of revoking Scottish football’s privileges to play during the coronavirus restrictions if clubs repeatedly broke the rules.
Justice minister Humza Yousaf wrote on Twitter: “Utterly unacceptable from Bolingoli. With a number of incidents, Scot Govt left with little choice but to consider whether pause is now needed in resumption of the game.
“Operational matter for Border Force & Police Scot, I support whatever enforcement action they deem necessary.”
There is uncertainty around Aberdeen’s home game against Hamilton on Wednesday given the spike of cases in the city.
A government spokesperson said: “The Scottish government is aware of reports of a Celtic FC player having broken quarantine rules last week.
“We are currently in discussion with the club and football governing bodies to establish the facts.
“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.”