The French league says it has viewed TV footage of some Bastia fans racially abusing Mario Balotelli during Friday night's match, amid complaints from the Nice striker that Ligue 1 officials did not act quickly enough.
This followed a statement on Saturday, when the French league said it would open an investigation after Balotelli had spoken out against Bastia fans he said made monkey noises at him.
On Saturday night, Ligue 1 said it had seen images of the abuse via television broadcaster BeIN Sports, "showing some Bastia supporters making racist insults toward Mario Balotelli."
The league said it: "Condemns with the strongest firmness those who took part in these actions, who have no place inside a football stadium."
In a brief statement said they deplored all of the incidents that happened on Friday.
Before the match, Nice's team bus had been pelted by stones as it arrived at the stadium.
Bastia responded to Balotelli's allegations by saying it was not aware of any such abuse taking place.
Early on Saturday, Balotelli wrote a message on his Instagram and Twitter pages, describing the abuse he heard during the 1-1 draw at the 20,000-capacity Armand Cesari stadium in Corsica and complaining that the French league had not acted swiftly enough.
"Is it normal that Bastia supporters make monkey noise (and) 'uh' 'uh' for the whole game and no one of the 'commissions discipline' say nothing?" Balotelli wrote, referencing the French league's disciplinary committee.
"So is racism legal in France? Or only in Bastia? Football is an amazing sport. Those people like Bastia supporters make it horrible!"
Balotelli, 26, the son of Ghanaian immigrants to Italy, concluded his post by writing in French that what happened was "une vrai honte," or a total disgrace.
Nice's official Twitter account shared Balotelli's message.
On their website, the French Riviera club threw its support behind Balotelli.
"Nice, which already had stones thrown at its bus before the game, is outraged by what happened to their players on Friday night, and in particular to Mario Balotelli," a statement read.
Balotelli joined from Liverpool on a free transfer in August and has scored eight league goals in 10 games to help Nice challenge for the title.
