Spanish prosecutors opened a probe on Monday into racist chants during a match aimed at Real Madrid's star forward Vinicius Junior as the club hit out at the country's football federation for failing to "prevent the situation".
The 22-year-old Brazil international was targeted by a home supporter during a 1-0 defeat at Valencia on Sunday and was later sent off.
The prosecutor's office in Valencia is investigating the incident as a possible "hate crime", a judicial source told AFP.
The move comes after Real Madrid said it had filed a complaint "in order that the facts be investigated and those responsible be held accountable".
The club said the chants, in its view, "constitute a hate crime".
Separately, Spain's government sports council said it was analysing the images to "identify the perpetrators of these insults and behaviours to propose the appropriate sanctions".
The body has in similar incidents in the past proposed a one-year stadium ban and fine of 4,000 euros ($4,300) for those found guilty.
Top figures from the world of football and beyond rallied around the player, who has frequently been singled out for racial abuse in La Liga.
The head of Spain's football federation, Luis Rubiales, said the country had a "problem" with racism.
"As long as there is just one fan, a single undesirable, or group of undesirables who hurl insults over someone's sexual orientation, or skin colour, we have a serious problem," he added.
But Real Madrid heavily criticised Rubiales in a scathing statement, saying that his refusal to ensure FIFA protocols, which suggest matches should be halted when racist abuse is heard, to be used in Spain is exacerbating the problem.
"His (Rubiales') inaction has resulted in the helplessness and defencelessness of our player Vinicius," said the club.
"The referees, instead of acting with decisiveness and applying the regulatory protocols, have chosen in the majority of the cases to abstain and avoid taking the decisions that corresponded to them."
During the match, Vinicius stood in front of fans behind the goal and pointed to the apparent culprit and play was delayed for several minutes in the second half.
Referee Ricardo de Burgos Bengoetxea spoke to stadium officials, who made an announcement calling for racist insults to stop before play resumed 10 minutes later.
The referee wrote in his post-match report that a fan shouted "monkey, monkey" at the player.
Vinicius was sent off in added time at the end of the game for hitting Valencia player Hugo Duro during a brawl.
He later issued a statement saying that La Liga "belongs to racists".
Real said the match officials "made unfair decisions based on incomplete images" when Vinicius was shown a red card.
Brazilian President Luiz Inacio Lula da Silva condemned the abuse, telling a news conference at the close of the G7 summit in Hiroshima: "He was attacked. He was called a 'monkey'."
He called for the Spanish league to take "serious measures".
Reacting on Twitter, Spanish Prime Minister Pedro Sanchez said there should be "zero tolerance for racism in football".
"Sport is founded on the values of tolerance and respect. Hatred and xenophobia should have no place in our football nor in our society," he said.
Also on Twitter, Labour Minister Yolanda Diaz, one of Sanchez's deputies, said "racist chants in football stadiums do not represent our country. We will continue to work to end racism".
Real Madrid coach Carlo Ancelotti said Spanish football needed to be prepared to halt matches.
"The Spanish league has a problem, and Vinicius is not the problem. Vinicius is the victim," Ancelotti said.
"What has happened today has happened before, but not like that, it's unacceptable," he told reporters.
FIFA reiterated on Monday that stopping matches is permitted as well as players walking off the pitch in their three-step approach when racist abuse takes place.
"Full solidarity with Vinicius," FIFA president Gianni Infantino said in a statement.
Vinicius has been racially abused at several stadiums this season in Spain and an effigy of him was hung from a bridge by Atletico Madrid fans.
La Liga have filed legal complaints to Spanish authorities on multiple occasions this season, with the league pledging on Sunday to do so again after investigating.
However, Ancelotti said it was not helping.
"What has happened? Reports, and nothing at all has come from it. The solution is to stop the game," said the veteran Italian coach.
Writing on Instagram, Vinicius said Spain was viewed in his homeland as "a country of racists".
Spain, he said, was "a great country, which welcomed me and that I love, but which has accepted to export to the world the image of a racist country.
"I am sorry for the Spanish people who do not agree, but today, in Brazil, Spain is known as a country of racists."
"The league that once belonged to Ronaldinho, Ronaldo, Cristiano (Ronaldo) and Messi now belongs to racists," Vinicius added.
La Liga argued it had been "proactive" in previous cases of racism against Vinicius, filing nine complaints with relevant authorities and prosecutors.