Thirteen people were killed and 70 hurt when an overpass carrying Mexico City metro train cars partially collapsed on to a road on Monday night, authorities said.
A video on local channel Milenio TV shows the overpass collapsing on cars on a road below, sending a train plunging down and trapping cars under rubble.
The accident left a preliminary toll of 13 dead and 70 injured, according to the city's Comprehensive Risk Management and Civil Protection Agency.
Mexico City mayor Claudia Sheinbaum travelled to the scene of the accident and said on Twitter: "Firefighters, public safety personnel are working. Various hospitals attending. We will give more information shortly."
Other videos on television stations and social media showed emergency medical crews and firefighters combing through the wreckage looking for survivors.
Mexico City Mayor Claudia Sheinbaum rushed to the area.
The accident happened at 10.30pm local time on the metro's Line 12, the construction of which has been plagued by complaints and accusations of irregularities.