Sunderland could face sanctions after it emerged that the club fielded an illegible player earlier this season.
The Black Cats, who have already received a fine from the Premier League for the error, played South Korean striker Ji Dong-won in four games before realising that he did not have international clearance to play.
Ji, who has since joined Bundesliga club Augsburg until the end of the season, featured in games against Fulham, Southampton, Crystal Palace and Manchester United.
Sunderland tonight responded to the claims, confirming to ITV Sport: "There was an administrative issue regarding the registration of the player. The club was fined by the Premier League and the matter was dealt with at the time."