(CNN) -- A judge on Thursday filed preliminary charges against Football Club Barcelona for alleged tax fraud in its purchase of Brazilian superstar Neymar, according to a copy of his writ viewed by CNN.
Judge Pablo Ruz at Spain's National Court expanded his investigation against the club, as requested a day earlier by a prosecutor, who alleged the club avoided paying 9 million euros (more than $12 million) in taxes on Neymar's signing and transfer, corresponding to contracts signed in 2011 and 2013.
The judge is already investigating whether a former Barcelona president committed financial irregularities in the signing of Neymar.
In a six-page order, the judge said the investigation would include a look at an alleged "contract simulation presumably carried out by the parties which signed the contracts."
The expanded investigation would hold FC Barcelona, a fan-owned club, responsible as an entity or business enterprise if found guilty of tax fraud, said a National Court spokesman, who by custom is not identified.
The judge ordered Spain's tax collection agency to examine FC Barcelona's tax filings for 2011, 2012 and 2013, the writ said.
Neymar joined Barcelona in June 2013, with his father -- who doubles as his agent -- having entered into an initial contract with the Spanish giants in late 2011.
In a statement on the club website, Barcelona on Wednesday said its "dealings with respect to this operation, and in light of all information available, was at all times in line with the relevant legal legislation."
Barca said its lawyers will appear in court "within the next few days in order to defend its interests and rights."
"We express our total willingness to collaborate with the justice authorities in this matter, as we have done since the issue arose," it added.
Barcelona's former president, Sandro Rosell, who resigned last month after a judge agreed to investigate a lawsuit against him for alleged irregularities in the Neymar deal, has denied any wrongdoing.
Ruz began the investigation last month after a legal complaint from one of the members of this fan-owned club.
Prosecutor Jose Perals on Wednesday formally asked the judge to expand the investigation. In an seven-page writ, Perals alleges that he's "become aware of a series of economic transactions by the club, and in favor of various companies, related to the signing of Neymar da Silva Santos Jr., based at times on simulated contracts."
The investigation originally came after season-ticket holder Jordi Cases complained that the amount paid to bring Neymar from Brazilian club Santos was more than the reported fee of 57.1 million euros.
A day after Rosell resigned, the club released figures that showed that Barca actually paid 86.2 million euros for Neymar.
Cases' lawyer, Felipe Izquierdo, earlier told CNN that other Barcelona executives, still working at the club after Rosell's resignation, also allegedly signed some of the contracts that brought Neymar to the club.
Barcelona has told CNN that one of those signatories was former club VP, and now President, Josep Maria Bartomeu.
Piers Edwards and Chris Murphy contributed to this report.