Investigation into whether or not Manchester City broke Financial Fair Play rules have begun, UEFA announced on Thursday.
If they are found guilty, the Premier League champions face a Champions League ban.
"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 regulations.
"The investigation will focus on several alleged violations of FFP that were recently made public in various media outlets," a UEFA statement read.
Last week, German magazine, Der Spiegel, leaked a new tranche of emails.
The messages provide more details of how City allegedly circumnavigated UEFA's Financial Fair Play rules.