Authorities in Argentina are investigating alleged tax evasion in the transfer of 444 footballers, with deals involving Manchester City's Sergio Aguero and Barcelona's Javier Mascherano among those under the spotlight.
"An investigation is under way concerning supposed (tax) evasion in transfers of footballers," a senior judicial source told AFP on Monday.
Other well-known players whose transfers are now under scrutiny include Pablo Zabaleta of Manchester City, Ever Banega and Pablo Piatti of Valencia, Martin Demichelis of Malaga and Diego Forlan, now of Internacional in Brazil.
However, the same source told AFP that the Federal Administration of Public Revenues (AFIP) will only be able to investigate any irregularities involving transfers of players from Argentina to foreign countries.
As a result, Aguero's move from Independiente to Atletico Madrid will be investigated, but not his subsequent move to City.
Similarly, Mascherano's switch from River Plate to Corinthians is also being examined, but not his later moves to England or Spain.
Financial operations involving footballers have become less and less transparent because of the growing proliferation of private investors and intermediaries who hold player registrations.
Among the cases which persuaded federal judge Norberto Oyarbide to ask the AFIP to investigate football transfers in the country was the sale of defender Jonathan Bottinelli to River Plate.
The 27-year-old moved across Buenos Aires from San Lorenzo, although a Chilean club was also involved in the deal.
"Irregularities were detected in several transfers involving first division players," said the AFIP last month.
"One of the most emblematic cases involved the strange sale of Jonathan Bottinelli to River Plate, in which a Chilean club held the registration of the player."
Because of their suspicions, the AFIP suspended 146 agents and asked for 12 players, including Bottinelli, to be stopped from playing until their situation has been clarified.
Oyarbide is also in charge of an investigation into the supposed falsification of European Union passports in order to facilitate transfers of Argentine players abroad.