Police raided UEFA headquarters today after its former secretary general and now FIFA president Gianni Infantino became embroiled in the Panama Papers affair.
Infantino is "dismayed" and "will not accept" that his integrity is being doubted after documents leaked from the Panamanian law firm Mossack Fonseca included a television rights contract bearing his signature.
The 46-year-old Swiss-Italian, in his former role as UEFA director of legal services, co-signed a television rights contract in 2006 with two businessmen who have since been caught up in football's corruption scandal, says the International Consortium of Investigative Journalists which is analysing 11m leaked files.
Infantino and UEFA deny wrongdoing, but Swiss authorities raided the Nyon offices of European football's governing body on Wednesday. UEFA said it would co-operate fully.
The Office of the Attorney General of Switzerland said the raid, which was one of two which took place on Wednesday, was part of criminal proceedings directed against persons unknown.
A statement from the Swiss OAG said: "On April 6, 2016, the Office of the Attorney General of Switzerland (OAG), within the scope of ongoing criminal proceedings, conducted a search on a co-operative basis for the collection of evidence at the headquarters of the UEFA and at another enterprise.
"The search was motivated by the suspicion of criminal mismanagement (Art. 158 of the Swiss Criminal Code / SCC) and, respectively, that of misappropriation (Art. 138 of the SCC).
"The OAG's criminal proceedings are in connection with the acquisition of television rights and are at present directed against persons unknown, meaning that for the time being, no specific individual is being targeted by these proceedings."
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 cooperate fully."
German publication Suddeutsche Zeitung obtained the Mossack Fonseca documents, with one showing Infantino in 2006 co-signed a contract on behalf of UEFA to sell television rights for the Champions League and other club competitions.
The deal was with two figures who have since been accused of bribery as part of the United States investigation into corruption at FIFA. Hugo Jinkis and Mariano Jinkis, his son, are currently under house arrest in Argentina.
Cross Trading, the Jinkis' Argentinian company which was registered in the South Pacific tax haven of Niue, bought the rights for US dollars $111,000, according to ICIJ.
The rights were immediately sold on to Ecuadorian broadcaster Teleamazonas for $311,170.
UEFA had initially denied doing business with any of the 14 individuals indicted by the FBI, but admits now its response was incomplete.
After a full 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.
While UEFA on Tuesday night referred to the story as "sad day for journalism" and Infantino also hit out at the reporting, the emergence of the story prompted Swiss law enforcement officials to act on other findings.
The OAG statement added: "The suspicion is based on the result of findings that have emerged from other proceedings, as well as the corresponding financial analyses carried out by the OAG.
"Current publications in the media subsequently revealed still other elements that made it possible to complement the existing findings in a decisive manner.
"The final impetus was provided in particular by confirmation on the part of the UEFA that it had concluded contracts with Cross Trading SA.
"The suspicion motivating these proceedings is linked to these contractual relations.
"The cooperative search was immediately undertaken for the purpose of securing evidence."
FIFA, prior to voting in Infantino as president on February 26, agreed to a reform package designed to address issues of governance, accountability, transparency and diversity.
But its troubled past continues to cast a shadow and provoke awkward questions.
Infantino has been urged to use the affair to show his commitment to implementing change.
Conservative Damian Collins MP, a founder of the group New FIFA Now which campaigned for reform under Infantino's predecessor Sepp Blatter, told Press Association Sport: "On issues like this Infantino needs to stand up and be counted, try to persuade people that he will drive through the reforms without fear or favour and radically change the culture and practices of world football.
"For FIFA's sake he's got to. His election was a step in the journey to reform, but only a small step and a lot more needs to be done."