Hosts Valencia and Real Sociedad have condemned the racist abuse aimed at visiting Japan international Take Kubo and forward Ander Barrenetxea during Sunday's match at the Mestalla stadium.
In a video posted by Sociedad on X, racist insults could be heard from the stands towards Kubo and Ander Barrenetxea, who was born in the city of San Sebastian in the Basque Country, while the players were warming up before being brought on.
The incident was reported to LaLiga straight after the match, Sociedad said in a statement on Monday.
Valencia condemned the racism, saying the actions of a few do not represent the values of the club.
"The club is at the disposal of the authorities for whatever they may require," Valencia said in a statement.
"If the individuals responsible are identified, the club will take appropriate measures, including imposing severe disciplinary action leading to their expulsion from Mestalla."
In June, the Magistrate's Court of Valencia issued the first conviction for racism in a soccer stadium in Spain following an investigation into racial slurs directed at Real Madrid's Brazil forward Vinicius Jr at Mestalla stadium.
Clubs and players have been outspoken about the issue with Vinicius saying in September that Spain should be stripped of its 2030 World Cup hosting rights unless significant progress is made in addressing racism in the country.
The Spanish Football Federation and LaLiga have taken steps to tackle an increase in racist abuse with measures including partial stadium closures, including at Mestalla.
The Spanish government joined an investigation after racist insults were allegedly directed towards Barcelona players at Real Madrid's Santiago Bernabeu stadium in October.