MEXICO CITY – Construction errors led to May collapse of a viaduct in the Mexico City metro which killed 26 people and injured dozens more, according to preliminary results of an independent investigation released by the city government on Wednesday.
The report, produced by the Norwegian risk management company DNV, suggests that the deficient welding of the metal studs, which were not properly welded to a steel beam that supported the railroad tracks, was among many mistakes that contributed to collapse.
The results corroborate the findings of a New York Times investigation that found shoddy construction on the subway line. Some of the posts that hold the structure together appeared to have failed due to poor welds, the Times found, a crucial mistake that likely caused the viaduct to fail.
Engineers consulted by The Times pointed to the presence of ceramic rings, or ferrules, left in place after the welding process as evidence of poor workmanship, a finding that was confirmed by DNV’s investigation.
In a statement, DNV said its report was based on “the field investigation and laboratory testing of samples from the accident” and that it “only contains the hypothesis of DNV at this point.” The full investigation will be completed later this year, the company said. The government of Mexico City, which hired DNV to investigate the causes of the crash, is also conducting its own investigation into the crash.
The results of the independent investigation could cause trouble for two of Mexico’s most powerful figures: Marcelo Ebrard, the foreign minister, and Carlos Slim, one of the richest businessmen in the world.
Mr Ebrard, the mayor of Mexico City during the construction of the line, wanted it to be completed before stepping down in 2012, according to several people who worked on the project. He is considered a powerful candidate to succeed President Andrés Manuel López Obrador in the upcoming Mexican presidential elections in 2024.
Mr Slim’s conglomerate, Group Carso, built Line 12, the part of the metro that collapsed. Line 12, Carso’s first rail project, aimed to expand the business into the lucrative sector.
Carso is currently building a significant part of Tren Maya, a 950-mile railway intended to support the economy of southern Mexico – one of the poorest regions in the country – and is the project he inherited from Mr. López Obrador.
Some engineers and architects working on the Tren Maya have complained about problems similar to those encountered during the construction of the metro: a rushed and disorganized process that does not have a master plan to guide the construction. And Mr López Obrador insisted he wanted the Tren Maya to be completed before he left office in 2024.