Manchester City's sponsorship deal with Etihad Airways will be analysed by Uefa's financial fair play (FFP) boss.
In a 10-year deal reportedly worth £400m, Etihad now sponsors both the club's shirt and the stadium.
But with City and Etihad sharing Abu Dhabi links, critics have claimed this is an attempt to circumvent European football's strict new financial rules.
City declined to reply, although the club have previously said speculation over the figures was "not accurate".
When asked what his reaction was when he first heard about City's deal, the chairman of Uefa's Financial Control Panel, Jean-Luc Dehaene, said: "I had some questions, yes.
"You know where the problems are and you know you will have to confirm them. But on the other hand they are all members of the ECA (European Club Association) and if they don't follow the rules they won't have the support of the other clubs.
"But it would be dangerous for our authority if we take judgements without facts."
The 71-year-old former Prime Minister of Belgium confirmed his panel would "benchmark" all deals to make sure they were "fair value".
"If we see clubs that are looking for loopholes we will act," he said.
"It is not enough to say 'we've got a sponsorship contract and that's OK' if the contract is out of line."
As well as the shirt and stadium, Etihad also sponsors The Etihad Campus which is being developed around the ground. This will create an expanded academy, sports science centre and training ground, as well as office and retail space and a 7,000-seat stadium for youth games.
All of this investment is exempt from the FFP rules as it is not deemed football-related. Any income accrued, however, does count.
In an exclusive interview with BBC Sport on Monday, City's chief executive Gary Cook said the deal was "unique".
"The Etihad Campus, which constitutes some 210 acres is unique in its breadth, depth and length of term," he said.
"It involves the tradition, which is shirt sponsorship, the naming rights of the stadium, but what we haven't seen in football is a campus, creating a place to be, to work.
"We've got a great relationship with Etihad. It's a long-term programme and they are equally very excited by it."
Cook added that City's recent spending was "not sustainable" but was needed to quickly attain Champions League football.
Manchester City have been the focus of intense scrutiny ever since an Abu Dhabi-based consortium led by Sheikh Mansour bin Zayed Al Nahyan bought the club in 2008.
The club made a loss of £93m in 2008-09, £121m in 2009-10 and last year's figures, due in September, are expected to be even worse, despite an increase in turnover partly due to a number of lucrative sponsorship deals with other Abu Dhabi-based companies.
Etihad Airways, for example, is owned by the Abu Dhabi government. The oil-rich state's ruler, Sheikh Khalifa bin Zayed Al Nahyan, is Sheikh Mansour's half-brother.