Public prosecutors in Brazil have started investigation into Barcelona's signing of Neymar last year.
In statement, the public ministry of Santos (MPF) - a branch of Brazil's public prosecutor's office - said it had sought information regarding the tax status of the company belonging to Neymar's father, N&N, reported Xinhua.
It added that documents sent by Brazil's tax office to the ministry had shown "the existence of tax debts".
"From the information already received by the MPF it is not possible to define the current state of the debt," the statement said.
The investigation centres on claims N&N received 40 million euros after Barcelona allegedly broke an agreement to wait until 2014 to sign the striker from Brazil's Santos.
The MPF also said it would consider collaborating with prosecutors in Spain, who are already probing the case following a civil suit by Barcelona fan Jordi Cases.
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The revelations come a day after Neymar Snr admitted to receiving a 10 million-euro down-payment in 2011 to guarantee his son's move to the Camp Nou.
But Neymar Sr denied any irregularities over the 21-year-old's signing last June.
The scandal last week prompted former Barcelona president Sandro Rosell to resign amid claims that Barcelona paid above the disclosed transfer figure and misappropriated funds.
Rosell and Barcelona have denied any wrongdoing, saying they paid 57.1 million euros for the Brazilian, as originally reported by media.