German magazine Der Spiegel made a number of claims against City last month in a series of articles based on documents purportedly attained from whistleblower Football Leaks.
Der Spiegel's reporting accused Sheikh Mansour's City regime of topping up multi-million pound sponsorship deals with Abu Dhabi companies, using its owner's fortune, in order to meet UEFA's FFP stipulations.
Further allegations claimed City was cut a favourable FFP settlement when it was punished for overspending by UEFA in 2014.
The Premier League champion dismissed the stories and said "the attempt to damage the club's reputation is organised and clear".
UEFA said soon after that it could re-open investigations should more information become available, and Ceferin this week referred to City's case as "concrete", with findings expected in the near future after media reports suggested a Champions League ban is a possibility.
"We are assessing the situation," he said. "We have an independent body working on it. Very soon you will have an answer on what will happen in this concrete case."
FIFA president Gianni Infantino was UEFA general secretary at the time of City's 2014 FFP settlement and defended the agreements reached with the club and Ligue 1 giant Paris Saint-Germain
"Our goal at UEFA was always to keep the clubs with us, not to kick them out, so you negotiate and seek solutions. That was my job as general secretary," he told Swiss publication Blick in November.
"The fact is, in the history of FFP, 30 violations have been detected. With all but one club there were agreements - agreements and negotiations are expressly allowed."