25 killed, 79 injured and many trapped in the rubble as metro overpass collapses in Mexico City
An elevated section of the Mexico City subway collapsed on Monday 3 May 2021, sending a subway car plunging toward a busy boulevard, killing 25 people including children and injuring about 79, who were hospitalised. At least two train carriages precariously hung from the damaged overpass. Initial rescue efforts saw medical and fire crews trying to access the carriages. The army was also in attendance. Mayor Claudia Sheinbaum said people were trapped inside the train, which was split in two and suspended. Video showed a car trapped under rubble, with dozens of rescuers searching through wreckage from the collapsed structure. The overpass was about five metres above the road in southern Mexico City. Hundreds of police and fire fighters cordoned off the scene in the southern borough of Tlahuac, as desperate friends and relatives of people believed to be on the trains gathered outside the security perimeter. Members of the Mexican Red Cross were also on scene to assist with the patients.
After the collapse, witnesses began rescue efforts and were later joined by first response teams. Neighbours offered the rescuers café de olla, water and bread. A shopping mall in the zone emptied their parking lot and let authorities set up a control post. After a few hours, rescue manoeuvres were halted since the structure was unstable. A crane was dispatched to hoist sections of the train while search and rescue teams worked to find survivors. The first railcar was removed the next day at 09h20 CDT and the second before 14h00 CDT later that day.
"A support beam gave way," Mayor Sheinbaum said, adding that the beam collapsed just as the train passed over it late on Monday. Rescue efforts were briefly interrupted at midnight because the partially dangling train was "very weak" and a crane had to be brought in.
Monday night’s accident was one of the deadliest in the history of the subway and questions quickly arose about the structural integrity of the mass transit system, among the world’s busiest. Of the 24 killed, 21 died at the scene, while the others died at hospitals. Only five have been identified so far. Children were among the fatalities, Sheinbaum said.
The collapse occurred on Line 12, the subway’s newest that stretches to the city’s south side. Like many of the dozen subway lines, it runs underground through more central areas of the city of nine million but is on elevated concrete structures on the outskirts.
A report issued by the subway system including photos in 2017 showed that the base of one vertical column supporting the tracks had cracked and shed layers of concrete because not enough steel rebar stirrups had been used when it was built around 2010. In 2017, authorities patched and widened the column by injecting resins, swathing it in carbon fibre, building a jacket of additional rebar around the base and pouring concrete around the collar.
Authorities also found that one of the horizontal beams had come loose from its support at the top of a vertical column and was sagging, the kind of failure that could have contributed to Monday’s collapse. Authorities at the time welded steel diagonal braces to the bottom of the beam, chipped out and repoured fractured concrete elements.
The collapse could represent a major blow the Mexican Foreign Relations Secretary Marcelo Ebrard, who was Mexico City mayor from 2006 to 2012 when the Line 12 was built. Questions about the quality of the construction emerged soon after he left office as mayor.
The Mexico City Metro, one of the largest and busiest in the world, has had at least two serious accidents since its inauguration half a century ago.
In March of last year, a collision between two trains at the Tacubaya station left one passenger dead, injuring 41 people. In 2015, a train that did not stop on time crashed into another at the Oceania station, injuring 12 people.
International engineering experts will be called in to help determine the cause of the collapse, which the country's foreign minister, Marcelo Ebrard, called "the most terrible accident we've ever had in the public transport system."
Sources: AAP – SBS, BBC, Reuters