Mexican fans of the Oakland Raiders chanted the gay slur ¡Puto! during the game between the Raiders and Houston Texans in Mexico City Monday night. The slur could be heard on the ESPN broadcast, growing louder as more of the stadium got in on the act as the game progressed.

The game was technically a Raiders home game and the crowd was heavily supporting Oakland. The chant had been heard at least a dozen times during the game on kicks: When the Texans tried a field goal; kicked off following a field goal and touchdown; attempted an extra point and on two punts. In addition to what was heard on ESPN, fans at the game were reporting hearing the slur.

The slur is a a regular occurrence at Mexican international soccer matches has gotten so bad that the national team asked fans not to chant it. FIFA, soccer’s governing body, has fined the team for the chant but nothing has stopped it. ¡Puto! is chanted when the opposing goalie does a free kick.

This was the first NFL regular season game in Mexico since 2005 and hearing this ugly slur was disgusting.

A source close to the NFL has told Outsports that the league was aware of the issue before the game and reached out to Azteca Stadium management to see what could be done. As we know from Mexico soccer matches, no one has figured out how to stop the chants — in-game announcements exacerbate the problem.

A spokesperson for ESPN had no comment.

In 2014 during the World Cup, I asked Andres Aradillas-Lopez, an economics professor at Penn State who was born and raised in Mexico, to explain why puto is a slur, since many deny it. Aradillas-Lopez is not gay. Here was his reply: