According to the city’s mayor, 49 people have been taken to hospital after the accident.
Emergency crews and firefighters have been searching the train for survivors.
The accident happened at 10.30pm local time (4.30am UK time) on the metro's Line 12.
The mayor said a support beam gave way as the train passed over it.
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Mexico City firefighters and rescue personnel work to recover victims from a subway car that fell after a section of Line 12 of the subway collapsed May 3. Photo: Hector Vivas / Getty Images
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