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 said called the case against City "concrete" and confirmed an "independent body" was working 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.