An non-Mexican fan suffered a heart attack just outside the Azteca Stadium shortly before the World Cup opener in Mexico City on Thursday between Mexico and South Africa.
The man was taken to hospital and police say his condition is stable.
Authorities in the Mexican capital initially gave no details on his nationality in a statement on X, but he is not Mexican.
The heat is expected to be a widespread problem for players and fans at the longest ever World Cup, which is being held by the United States, Mexico and Canada. Mexico City is also at altitude.
