Five Republic of Ireland players will miss this afternoon's Nations League clash with Wales after one squad member tested positive for Covid-19.
It has also emerged that the positive Covid-19 test returned by an unnamed FAI staff member prior to Thursday's Euro 2020 semi-final play-off against Slovakia may have been a false positive.
That incident ruled strikers Aaron Connolly and Adam Idah out of the game, which Ireland lost after a penalty shootout.
The two players had moved seats on the aircraft bringing the Ireland squad to Slovakia and were deemed to be in close contact with the staff member who then returned a positive Covid-19 result.
However, following further testing in Dublin ahead of the Nations League encounter today and the game in Finland on Wednesday, a squad player has tested positive following two tests.
As a result of this, four other squad members deemed to be close contacts under HSE guidelines will miss this afternoon’s game.
The FAI said in a statement: "Stephen Kenny's Ireland squad has received one positive Covid-19 test result ahead of today’s Nations League game against Wales at the Aviva Stadium, after the latest round of UEFA testing.
"A player – who cannot be named at this time - tested positive on Friday after a negative test on Monday but his case is not related in any way to that of the backroom team member who tested positive on Monday last.
"Talks with the HSE late last night identified four other players as close contacts of this positive case and they have been stood down from the matchday squad for today’s game against Wales."
They added: "In a separate development, the FAI can now reveal that the staff member who tested positive for Covid-19 in Bratislava on Wednesday, may have received a 'false positive' result.
"Two further tests carried out on the individual on Saturday have confirmed no trace of Covid-19. The HSE and UEFA have been informed of this result. The FAI will now discuss the issue with UEFA.
"In light of these developments, the FAI wishes to make it clear that it complied with all UEFA and HSE Covid-19 guidelines concerning the availability of players and the well-being of staff around the Slovakia v Republic of Ireland fixture in Bratislava on Thursday night."
Ireland are due to fly to Finland ahead of a match on Wednesday.
The association concluded: "Manager Stephen Kenny will review his options for Wednesday's UEFA Nations League game in Finland after today’s fixture against Wales.
"The FAI will review all Covid-19 protocols with UEFA and the HSE after the Finland game."