Gonzalez denies the accusation. But in Neymar's native Brazil, the ministry responsible for human rights issues said it stood behind the world's most expensive footballer.
"In the face of yet another case of racism that has come to the surface in sport, the ministry of women, the family and human rights publicly voices its solidarity with the player Neymar Jr," the ministry said in a statement. "Racism is a crime."
The statement came after Brazilian President Jair Bolsonaro on Monday retweeted Neymar's own version of events.
The Brazilian striker slapped Gonzalez on the back of the head near the end of Sunday's match, sparking a mass brawl that ended with five players sent off, including Neymar.
He now faces a potential multi-match suspension, as does Gonzalez, if league officials find Neymar's accusation is true.