As part of a shocking update, official sources stated a 19-year-old woman was among those to tragically lose her life as crowds descended on the city following the country's 2-0 victory over Ecuador.
A 48-year-old woman and a 44-year-old man also died, as over a million of fans congregated - mainly at the Angel of Independence monument in the centre of the city - to mark Mexico's first World Cup knockout win since 1986.
Health officials stated all three were rushed to hospital for emergency treatment but were later confirmed to have died from suffocation and were identified by their families
City Mayor Clara Brugada expressed her "most sincere condolences" to the families and urged fans to "always celebrate with responsibility, care, and empathy" ahead of Mexico's next game.
Brugada also asked supporters not to gather in public areas where large crowds historically tend to build up to avoid any further emergency incidents or loss of life.
Over 20 million people live in Mexico City's metropolitan area - as one of the most densely populated places in the world - and the warning comes as Mexico prepare to face either England or DR Congo in the last 16 on July 6th, in a return to the Estadio Azteca.