A Spanish court said on Wednesday it had opened a tax probe into Doyen Sports, whose football funding schemes and third-party player ownership activities were exposed by Football Leaks.
The court said the firm, founded in 2011 in Malta and since closed down, is suspected of fraud worth at least five million euros.
Doyen used a "complex structure" to hide from tax authorities the fact that it was managed from Spain, not Malta, Spain's High Court which is carrying out the probe said.
Doyen, at the heart of damaging leaks made by Portuguese hacker Rui Pinto who broke into the company's computers, could have earned profits of 20.5 million euros ($23 million) between 2013 and 2016 from the management of players, the court added.
It could have gained another 1.3 million euros between 2013 and 2015 from loans to clubs such as La Liga sides Atletico Madrid and Sevilla, the court said.
In 2013 alone it is suspected of having defrauded Spain's tax office of more than five million euros.
The total amount which was defrauded could be higher "once all the precise information" about the firm's activity is analysed.
The court said the company and its manager, Nelio Freire, are accused of tax crimes while four others are accused of tax fraud and money laundering. They have all been summoned for questioning.
In Spain the company loaned money to clubs in return for a percentage of the fees they get when a player is transferred. It also made money from the management of a player's image rights and the trade in economic rights to players.
The court said it was involved in the sale of the rights of former Atletico forward Radamel Falcao as well as the purchase of 50 percent of the rights of Valencia midfielder Geoffrey Kondogbia.
IN 2015, FIFA ruled third-party player ownership was illegal, and banned all future deals of the nature in football.