Antoine Griezmann's controversial move from Atletico Madrid to Barcelona will reportedly be investigated by the Spanish Football Federation.
Griezmann joined the La Liga champions earlier this week, finally completing a protracted move that was first mooted last summer.
Barcelona claim to have activated a clause in the Frenchman's contract which allowed him to leave for €120million from July 1.
But Atletico claim their rivals began negotiating with Griezmann as far back as March, meaning they are owed another €80m due to a previous clause in his contract.
The club themselves are yet to make an official complaint, but according to reports in Spain, the federation has opened a file on the move regardless.
Barcelona have consistently denied any wrongdoing with club president Josep Maria Bartomeu saying: "I have spoken to them, but I do not think there is any proof, because there is no evidence of anything.
"I understand everyone defends their interests and I've spoken to [Enrique] Cerezo [Atletico president], but I don't see that the case can evolve in a positive way for them. There's nothing.
"We contacted Griezmann after he made the video saying goodbye to the fans, there was nothing in March."
The player himself added: "Regarding Atletico, it's a pity. I went to see them on purpose so they would not be caught off guard and could prepare for the future."
Griezmann was linked with a move to Barcelona last summer but decided to remain at Atletico before making the opposite decision this summer.
His place in Diego Simeone's side has been taken by young starlet Joao Felix who joined for €130m from Benfica.
Atletico beat off competition from some of the world's biggest clubs to land the forward, including Manchester City .
