The GAA have have cancelled a number of tickets for the All Ireland Football semi final meeting of Dublin and Tyrone game after they appeared on websites at above cost price.
Reports have emerged that tickets, which cost €45 and €30 respectively, were changing hands on the internet for as much as €145 - more than three times the original price.
The GAA have asked such sites to remove any tickets they may have listed, and urged supporters not to buy tickets from unauthorised sellers.
The GAA have also indicated that stand tickets for Sunday’s All-Ireland SHC semi-final between Cork and Waterford are likely to sell out.
They are on sale through the Association’s website and other outlets.
Meanwhile, Meath official David Coldrick will referee the game while the other semi final between Kerry and Mayo will be refereed by Maurice Deegan.