Swiss police have raided UEFA's offices after its former secretary general and now FIFA president Gianni Infantino became embroiled in the Panama Papers scandal.
Documents leaked from Panamanian law firm Mossack Fonseca reportedly show he signed a contract on behalf of UEFA to sell TV rights for the Champions League and other club competitions.
Mr Infantino, in his former role as UEFA director of legal services, co-signed the contract in 2006 with two businessmen who have since been caught up in football's corruption case, according to the International Consortium of Investigative Journalists (ICIJ) analysing the 11 million leaked files.
Both UEFA and Mr Infantino deny any wrongdoing.
The 46-year-old Swiss-Italian said he is "dismayed" and "will not accept" his integrity is being doubted.
UEFA said in a statement: "UEFA can confirm that today we received a visit from the office of the Swiss Federal Police acting under a warrant and requesting sight of the contracts between UEFA and Cross Trading/Teleamazonas.
"Naturally, UEFA is providing the Federal Police with all relevant documents in our possession and will co-operate fully."
Mr Infantino's alleged deal was with Hugo Jinkis and his son Mariano Jinkis, who have since been accused of bribery as part of the US investigation into corruption at FIFA.
Both are currently under house arrest in Argentina.
Their Argentinian company Cross Trading was registered in the South Pacific tax haven of Niue, and bought the TV rights for $111,000 (€97,479), according to ICIJ.
The rights were immediately sold to Ecuadorian broadcaster Teleamazonas for $311,170 (€273,267).
UEFA had initially denied doing business with any of the 14 individuals indicted by the FBI, but now admits its response was incomplete.
After a review of thousands of commercial contracts, it accepts the deal was done as part of an "open tender" - a process conducted by Team Marketing on behalf of UEFA - and the rights were sold to the highest bidder.
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