Ronaldinho and his brother, Roberto, have been detained by police in Paraguay after entering the country with a fake passport.
The Brazilian entered the country on Wednesday for a charity event.
Officials then came to his hotel suite near the capital of Asuncion and found the documents.
They found that his passport, as well as Roberto's, said that they were from Paraguay and not Brazil.
Ronaldinho is currently without a Brazilian passport after having his seized because of an environmental issue in 2018.
There have been reports that Ronaldinho has been arrested but that is not the case.
Instead, ESPN have noted that he and his brother have been detained by police.
They have been allowed to stay at the hotel but remain under custody by authorities. They must also report to the prosecutor's office on Thursday morning.
They could still be arrested if an investigation goes against them, though.
"[Ronaldinho and his brother] are still under judicial investigation and they have to testify. Then it will be decided whether they will be arrested or not," Paraguay's interior minister Euclides Acevedo told ESPN Brasil.
A man has been arrested in connection with the passports. Ronaldinho and his brother are said to be cooperating in the investigation and have claimed they "were tricked" by the man arrested.