UEFA have opened a formal investigation into Manchester City over a potential breach of Financial Fair Play regulations.
Internal club documents regarding City's business have previously been published via the Football Leaks series from German news outlet Der Spiegel.
In the most severe cases of breaking the Financial Fair Play rules, UEFA can ban clubs from competing in the Champions League, Europe's elite club competition.
UEFA released a statement on Thursday, which reads: "The Investigatory Chamber of the independent UEFA Club Financial Control Body has today opened a formal investigation into Manchester City FC for potential breaches of Financial Fair Play (FFP) regulations.
"The investigation will focus on several alleged violations of FFP that were recently made public in various media outlets.
"UEFA will make no further comments on the matter while the investigation is ongoing."
Spiegel previously alleged City officials had misled UEFA by hiding the source of revenue from sponsorship deals linked to the club's owners in Abu Dhabi.
The Football Association is currently investigating claims City paid £200,000 to Jadon Sancho's agent when the current Borussia Dortmund winger was 14.
UEFA also found City guilty of breaching FFP rules in 2014, when the club accepted a conditional £49m fine and restrictions on their European squad and incoming transfers.