The SFA have explained Bobby Madden's surprise Premiership withdrawal just hours before he was due to take charge of Ross County vs Celtic and revealed it was Covid related.
Madden was the appointed match official for the Sunday night clash but a late change saw him removed from the game.
The FIFA official was replaced by fourth official David Munro, with Billy Baxter stepping in to take over in the technical area.
Madden had just returned from taking charge of the Eternal Enemies Derby between Olympiacos and Panathanaikos in Piraeus last weekend.
And it transpires that one of the linesmen that travelled with him to Greece, David Roome, returned a positive Covid-19 test on Wednesday - with Madden considered a close contact despite his own pair of negative tests in the following days.
Another assistant involved in the trip to Athens, Graeme Stewart actually ran the line at Saturday's match between Hibernian and Hamilton Accies despite the fact he should have self-isolated - prompting an apology to both clubs.
SFA chief executive Ian Maxwell said: "While the circumstances are complex the reality is that under Scottish Government guidelines all match officials involved in the trip should be considered close contacts.
“I have reiterated that the positive case and subsequent contact tracing should have been undertaken in line with the Scottish Government’s guidelines and the established system utilised by ESCAG.
“I have tonight apologised to Hibernian and Hamilton Academical for the unnecessary risk of having an assistant referee at a match when he should have been self-isolating, however much it is mitigated by two negative tests in the build-up to the match.
“As part of an internal review, I have asked the respective departments to ensure we maintain the highest standards of compliance relevant to Scottish Government protocols.”
