Chelsea Football Club has been accused by Fifa of breaking rules while signing 25 minor foreign players, according to a Guardian report.

The number of such cases could rise as world football’s governing body continues to investigate the club’s transfers. The Premier League defending champions could attract sanctions, including a transfer ban, the report said.

Fifa had announced last September that it was investigating Chelsea with respect to the transfers of minor players from foreign countries. According to Fifa’s transfer rules, clubs are not allowed to sign overseas players under the age of 18 unless their parents have emigrated for reasons not connected to football, and some other exceptions.

The investigation against Chelsea was triggered by the London-based club’s acquisition of 18-year-old Bertrand Traore from Burkina Faso in January 2014. Fifa later found out that Traore had played for Chelsea in a non-competitive game more than two years before the transfer was officially announced in 2014.

Clubs such as Atletico Madrid, Real Madrid and Barcelona have already received transfer bans for similar breaches. Chelsea chose not to respond directly to the accusations, instead just telling the daily, “Chelsea FC complies with all Fifa statutes and regulations when recruiting players.”