The contract, reportedly signed by current FIFA President Gianni Infantino in 2006 when he was UEFA legal director, was leaked from the database of Panama-based law firm Mossack Fonseca.
UEFA says it "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."
European soccer's governing body says it "is providing the Federal Police with all relevant documents in our possession and will cooperate fully."