Two hosts of the Spanish-language US broadcaster Telemundo were suspended after racist gestures when the South Korean victory over Germany was celebrated.
The victory meant that Mexico was free for the tournament.
During a festive dance on the set, the two presenters saw their eyes stand crooked.
The same gesture was posted by several Mexican fans on Twitter to thank South Korea.
Social media users denounced the instances as racist and many Mexicans have since apologized.
South Korea's victory over Germany at the FIFA World Cup meant that Mexico finished second in their group, knocking it into the knockout stages.
South Korea failed to advance to its next stage despite its victory, but its fans joined forces with Mexican fans around the world to celebrate.
In Mexico City, hundreds of fans rushed to the South Korean Embassy to celebrate with the staff and Consul General.
However, part of South Korea's excitement became bitter as Mexican fans "thanked" the Koreans by pushing images of themselves to the side, which is considered a racist gesture.
Korean fans soon started using the hashtag #Racial Discrimination to express their frustration.
Another tweeted that South Koreans need "no brothers who are racists" .
Some were somewhat more lenient in their reaction, arguing that while the gesture was wrong, Mexican fans might not want to offend.
" They did it because they did not know it was racist. You can smile and explain the meaning to them, you do not have to be mad at things if done without evil intentions." Person wrote (in Korean).
Many Mexicans writing a weird picture removed them in response to criticism.
"A mixture of frustration and anger"
Minji Lee, BBC News Korean, Seoul
The oblique eye movement is nothing new for Koreans. The Telemundo incident is the youngest in the series. While the broadcaster reacted quickly, the general feeling is a mix of frustration and anger at this recurring trend and helplessness to not be able to stop it.
Will the continuing cycle of these racist gestures followed by local outcry educate people What is a racist gesture and what is not?
It seems that some Mexicans and people in the Latin America region have apologized and admitted that it is wrong. At the same time, the incident has also caused some Koreans to look back on their own words and deeds.
A Twitter user wrote, "The gesture of saying was racist, it's okay, but if you go beyond that and start to [to Mexicans that] you'll even be looked down on by the US, then you'll become a racist yourself."
Telemundo, part of NBC, issued a statement saying he was "extremely disappointed" in the two moderators James Tahhan and Janice Bencosme.
"Our company takes this kind of inappropriate behavior very seriously because it contradicts our values and standards," it said.
The broadcaster said both moderators had been "suspended indefinitely".
James Tahhan also apologized on Twitter saying that he "made an inappropriate and insensitive gesture to the Asian community."
He said he "wants to apologize to anyone who gets upset about it."
The Miami-based station broadcasts Spanish to the Hispanic population of the United States, including the large Mexican community.
Many Twitter users pointed out that a network that addresses itself to a minority exposed to racism in the US should be more sensitive to other minorities.
While some users argued that the gesture may not have been malicious, others insisted that it was known in Latin America as an insulting gesture.
Homophobia and racism
Mexican fans at the World Cup in Russia had already provoked controversy in earlier group games with homophobic chants.
Fifa has opened an investigation into the case and may have disciplinary action.
His compatriot, football legend Diego Maradona of Argentina, was also accused of making the same racist gesture to Asian fans at the World Cup in Russia.
Although the incident was not caught by the camera, the football star later apologized on Facebook, arguing that he was only happy to see "an Asian boy wearing an Argentine T-shirt."