The Mexican Soccer Federation issued a statement Tuesday condemning violence among fans, after one Mexico fan stabbed another at a Sunday match.
The violence occurred at a stadium in Santa Clara, California, where Mexico's national team lost 1-0 to Qatar.
Video of the attack showed several Mexico fans scuffling in the stands. Another fan, also wearing a Mexico jersey, approached with a knife and stabbed one of the men involved in the scuffle.
The wound appeared to be near the man's neck or upper torso, and it could be seen spurting blood.
The federation issued a statement to "roundly condemn these acts of violence," and it offered to work with local authorities to avoid such events in the future.
Both Qatar and Mexico advanced to the quarterfinals of the Concacaf Gold Cup. The United States, which beat Mexico in the Nations League semifinals in June, is also in the quarterfinals, as is Group A second-place finishers Jamaica.