Manchester City are under investigation for potential breaches of UEFA's Financial Fair Play (FFP) regulations, the governing body of European football has announced.
UEFA released a statement confirming the Premier League champions were being looked at, and noted the alleged violations have been made known via media outlets.
"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 UEFA statement reads.
"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."
German magazine Der Spiegel made multiple accusations against Man City last year in a series of articles that were based on information obtained from whistleblower organisation Football Leaks.
The publication claimed Sheikh Mansour's City regime topped up multi-million pound sponsorship deals with Abu Dhabi companies, using their owner's fortune, allowing them to meet UEFA's FFP regulations.
Man City have denied any wrong doing when commenting on the Der Spiegel reports, claiming "the attempt to damage the club's reputation is organised and clear".
In light of UEFA's statement, the Premier League champions have responded by welcoming the investigation and denying any financial violations.
"Manchester City welcomes the opening of a formal UEFA investigation as an opportunity to bring to an end the speculation resulting from the illegal hacking and out of context publication of City emails," the club wrote.
"The accusation of financial irregularities are entirely false. The club’s published accounts are full and complete and a matter of legal and regulatory record."
In December, UEFA president Aleksander Ceferin called the case against City "concrete" and confirmed an "independent body" was working on the investigation.
At the time, reports suggested that if Man City were found to have violated FFP, the club could face a ban from the Champions League.
City are known to have violated FFP in the past, having reached an agreement over a settlement in 2014 with then-UEFA general secretary, now FIFA president, Gianni Infantino.
Der Spiegel also claimed Man City and Paris Saint-Germain received favourable terms for that settlement by Infantino.