The World Cup qualifier against Andorra goes ahead in Barcelona after a bizarre pre-match personnel inspection.
The Football Association of Ireland had passed on to Fifa a tip received from an anonymous source that up to six members of the Andorra squad are not truly eligible.
And on Tuesday official Fifa match commissioner Leon Walker insisted on visiting both squads in their hotels and ordered all players to line up with their passports open on the picture page.
Bernard O'Byrne, the FAI's chief executive, said: "It is a most unusual procedure but we've never really had any reason to believe anything was wrong.
"Having received the information, albeit from an anonymous source that we could not check, we felt obliged to pass it on to Fifa and let them deal with it ahead of the match.
"We just wanted to ensure there was no possibility of becoming embroiled in something after the game."
Naturally, the Irish are more than a little circumspect about eligibility questions, drawing as they do on many English-born players with Republic parentage and grand-parentage.
It has always been a controversial subject and gained sharper focus recently when retired striker Tony Cascarino admitted in his autobiography that he knew he did not have genuine Irish connections despite winning for than 80 caps.
This time, though, it was the opposition under scrutiny.
Andorra, an independent sovereign state since 1993, have several players who have previously represented Spain at junior competitive level among their ranks.
However, they have pointed out that Fifa granted special dispensation to Andorra to adopt specified players who previously had only Spanish qualifications in football terms and this has now been confirmed by the football's world governing body.