The Premier League has confirmed it will investigate an alleged leak of Cardiff's team details ahead of their match with Crystal Palace.
Chairman Mehmet Dalman informed the Premier League about the claims.
"The Premier League has received a formal complaint from Cardiff City and will now investigate the matter," confirmed a league spokesman.
The Bluebirds say Crystal Palace, who won the game 3-0, knew their line-up 24 hours before kick-off,
Cardiff City are taking disciplinary action against two employees.
The 5 April defeat by Palace left Ole Gunnar Solskjaer's side 19th, a position they continue to hold despite a 1-0 victory at Southampton last weekend.
The disciplinary action does not involve players, but the club considers the leak to be a "sackable offence".
Crystal Palace chairman Steve Parish declined to comment on the grounds that he did not want to give the accusations "oxygen".
Solskjaer also chose not to talk about the allegation specifically, but categorically denied suggestions that a player had been involved.
Club captain Steven Caulker said he was "frustrated" because the row could be a distraction from the fight to avoid relegation.
"To be honest, there's been things like that all season where certain things have been leaked," Caulker said.
However, the centre-back later clarified that he was referring to "leaks" about matters other than team selection.
"For me it's frustrating because we need to focus on what's going on on the pitch and not what's happening off the pitch," Caulker added.