The impact of the leaked documents from a Panamanian law firm is snowballing, with Iceland facing a political crisis after its prime minister stepped aside on Tuesday following revelations about his wife's finances.
Recently elected Infantino joined a growing list of public figures and political leaders whose financial arrangements have come under scrutiny after the release of the 11.5 million documents, which have caused public outrage over how the rich and powerful can hide money to avoid taxes.
Infantino said he was "dismayed that his integrity was being doubted" by media reports which said the contract he signed several years ago as a UEFA official sold broadcast rights at a low price to a company which sold them on at a far higher price.
Reuters, which has not seen the documents, was unable to confirm this and UEFA denied that the rights were sold at below the market price.
"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," UEFA said in a statement.
Infantino said in a FIFA statement the contract had been "properly conducted" by UEFA.
British Prime Minister David Cameron also faced another day of questions about his finances, because his late father was among the tens of thousands of people named in the documents from law firm Mossack Fonseca, which has denied any wrongdoing.
After having at first described it as a private matter, Cameron's office said on Tuesday that he and his family did not benefit from any such funds at present. Cameron also said he did not own any shares or have any offshore funds.
But his failure to say whether he or his family would benefit in future only intensified media speculation, with the story splashed across many newspaper front pages on Wednesday.
"There are no offshore funds or trusts which the prime minister, Mrs Cameron or their children will benefit from in future," a spokesman for Cameron said on Wednesday.
Among those named in the documents are friends of Russian President Vladimir Putin, relatives of the leaders of China, Britain and Pakistan, and Ukrainian President Petro Poroshenko.
Poroshenko said he set up an offshore trust to separate his business and political interests after he became president and the arrangements were carried out with full transparency. He said he was not trying to minimize tax payments.
"There does not need to be an investigation," Poroshenko told reporters in Tokyo, when asked about the planned investigation by Ukraine's fiscal services.
Iceland suffered further political fallout from the documents, with the government hoping to avoid early elections by trying to pick a prime minister to replace Sigmundur David Gunnlaugsson.
He stepped down after the documents showed his wife owned an offshore company that held millions of dollars worth of debt from failed Icelandic banks. Gunnlaugsson has said his wife's assets were taxed in Iceland but the opposition has accused him of a conflict of interest because his government was negotiating deals with claimants on the banks. It was not clear whether Gunnlaugsson's wife had received any payment from the banks.
Icelanders, already angry with the financial and political elite after the 2008 banking crisis wrecked the economy, were expected return to the streets on Wednesday. Protesters pelted parliament with yoghurt and eggs earlier this week.
Other leading figures and financial institutions responded to the leak with denials of any wrongdoing as prosecutors and regulators began a review of the investigation by the U.S.-based International Consortium of Investigative Journalists (ICIJ) and other media organizations.
Britain, France, Australia, New Zealand, Austria, Sweden and the Netherlands are among nations that have started inquiries.
In the Netherlands, the chairman of law firm Ploum Lodder Princen (PLP) that reportedly helped wealthy individuals set up shell companies in Mexico and Ecuador to channel cash flows offshore, stepped down.
PLP said it had sought an independent inquiry by the Dutch Financial Supervision Office but could not "identify itself in any manner with the accusations which have been brought forward in this publicity."
French Finance Minister Michel Sapin said he had questioned the head of Societe Generale bank about its record creating shell companies and opening client accounts in Panama.