Scotland boss Steve Clarke has explained the process which led to Ryan Christie and Kieran Tierney being ordered to self-isolate for two weeks.
The players, along with two members of staff, were forced to step away from the Scotland squad after being defined as close contacts of Stuart Armstrong, who returned a positive COVID test this week.
Armstrong is required to self-isolate for ten days from the date of his test, while Christie and Tierney are each required to do so for 14 days. This rules Christie out of next weekend's Old Firm match at Parkhead.
Scotland boss Clarke explained: "I heard the news early in the morning Stuart had tested positive. From then it was a continual update throughout the day on how that affected the rest of the squad.
“We had to work out who Stuart had been in close contact with, with the NHS Track and Trace getting involved.
“They narrowed it down to the amount of time he had in each other’s company. And unfortunately that robbed us of another two players, as well as two members of staff.
“The testing procedure is there. We all got tested when we first arrived on camp. For that one Stuart tested negative, funnily enough.
“But the UEFA test was done on Tuesday and when the results came in this morning everyone was negative except Stuart. That’s the nature of testing people and why we do it. From there the procedures kick in and Dr John MacLean and Graeme Jones are the people who kick into action.
“The NHS came in and found the distances and made their decisions from there.”
Celtic say they want to hold talks with the Scottish Government to "fully understand the self-isolation procedures for players who continue to deliver negative test results, as Ryan as".
Christie added: “I am so disappointed by the events of today and the potential effects this could have on my country and club. As I have operated within these protocols for such a long time now, I am well aware of all the rules and social distancing from team mates has become the norm and something I have observed.
"The situation is very frustrating, particularly as I don’t believe I have done anything wrong.”
Celtic earlier said: "Clearly we are disappointed and frustrated to learn of today’s news, however, our over-riding concern is of course the health of the players and staff concerned.
"It is of course disappointing that this has arisen during the international break but it is something which shows the many challenges clubs currently face. Celtic’s rigorous testing programme continues.
"The Celtic squad based at Lennoxtown have all again returned negative test results today [Wednesday]. In addition all other players currently on international duty, outwith Odsonne as reported yesterday, have reported negative tests."
