Twenty people have been killed, including children, and 49 hospitalised when an elevated metro line collapsed onto a busy road in Mexico City on Monday night.
Rescue efforts for potential survivors were paused shortly after the accident, authorities said, because of the risk that more of the Metro overpass and train cars could slam down onto the road.
Carriages were seen hanging from the overpass in a tangle of twisted cables with the ends pointing towards the ground in a V-shape.
“Unfortunately there are 20 people dead so far,” including minors, Mexico City Mayor Claudia Sheinbaum told reporters at the scene in the south of the capital.
The city’s civil defense department said on Twitter that around 70 others were injured in the dramatic accident, one of the worst to strike the Mexico City metro since it was inaugurated in 1969.
Security camera footage broadcast by local media showed the carriages plunging towards the ground.
Dozens of emergency workers were seen trying to rescue victims from the carriages.
But the work later had to be paused because of fears the wreckage was too unstable.
“For now the rescue has been suspended because the train is very weak. A crane is coming to continue” the work, Sheinbaum said.
A car was trapped under the rubble, but a person inside the viaduct managed to get out alive, she said.
“Suddenly I saw that the structure was shaking,” an unidentified witness told the Mexican television network Televisa.
“When the dust cleared we ran… to see if we could help. There were no screams. I don’t know if they were in shock,” she added.
Medics were seen taking the injured away on stretchers.
The casualties were rushed to different hospitals in the city, Sheinbaum said.
The accident occurred when a section of the elevated tracks collapsed at the Olivos station at around 10:00 pm (0300 GMT), she said.
The Metro 12 line that runs over the collapsed overpass was built almost a decade ago when Foreign Minister Marcelo Ebrard was mayor of Mexico City.
“What happened today with the Metro is a terrible tragedy. My solidarity is with the victims and their families,” Ebrard said on Twitter.
“Of course, the causes must be investigated and responsibilities defined.”