The offices of European football's governing body UEFA have been searched by Swiss police.
They have seized information about a contract disclosed in the Panama Papers that was signed by former UEFA general secretary Gianni Infantino, now head of the global football body FIFA, according to the BBC.
Infantino has denied wrongdoing, while UEFA says it is helping police.
Meanwhile, a FIFA ethics committee official named in the papers – Juan Pedro Damiani – has resigned.
Leaked documents suggest the Uruguayan and his firm provided legal assistance for at least seven offshore companies linked to Eugenio Figueredo.
A former FIFA vice-president, Figueredo was among 14 people arrested in Zurich last May as part of the U.S. inquiry.
The office of the Swiss attorney general said the search of UEFA offices in Nyon was part of "ongoing criminal proceedings" and had been launched because of "suspicion of criminal mismanagement and... misappropriation."
It added that criminal proceedings "are in connection with the acquisition of television rights and are at present directed against persons unknown."
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While at UEFA, Infantino co-signed a television rights deal in 2006 with two businessmen who have since been accused by the FBI of bribery.
Cross Trading – owned by Hugo Jinkis and his son Mariano – bought TV rights for UEFA Champions League football in 2006 for $111,000 and immediately sold them to Ecuadorian broadcaster Teleamazonas for $311,170.
Cross Trading also paid $28,000 for the rights to the UEFA Super Cup, selling those to Teleamazonas for $126,200.
The contract came to light after 11 million documents were leaked from Panamanian law firm Mossack Fonseca.