A probe of construction defects in the cavalcade caused the accident that left 26 people dead, a probe found.
An investigation into the Mexico City subway disaster revealed a series of construction defects in the collapsed cavalcade, killing 26 people and induces angry demands for justice.
The first report released Wednesday by Norwegian engineering company DNV said a structural failure had caused the elevated section to collapse on May 3, dropping a passenger train.
Preliminary results, which were presented at a press conference by Mexico City authorities, identified a number of shortcomings in the construction process.
They include “unfinished and / or poorly executed welding”, insufficient bolts and the use of different types of cement.
Experts have also found deformities and fractures in the bundles of the section that collapsed, injuring dozens of people and provoking accusations of negligence by devastated relatives.
The metro line, the newest in the city, has been plagued by problems since it opened in 2012.
DNV, which has been hired by authorities to investigate the causes, plans to broadcast two more reports on July 14 and August 30, its Mexican director Eckhard Hinrichsen told the news conference.
The probe aims to establish whether the design and materials were suitable, whether construction was done in line with the design, and whether operation and repairs were factors in the crash.
Prosecutors are also investigating the disaster, but have also released their findings.
Mexico City Mayor Claudia Sheinbaum said she will put in place a technical team to reinforce and repair the 24.5 km (15-mile) line.
Fury over the crash has flooded two of President Andres Manuel Lopez Obrador’s political supporters and key contenders to be his left-wing party’s candidate in the 2024 presidential election.
Sheinbaum is questioning whether the network has been properly maintained since it took office in 2018.
Foreign Minister Marcelo Ebrard oversaw the development and inauguration of the line in his former position as mayor of Mexico City from 2006 to 2012.
Ebrard said his administrative responsibility for the project ended when he left the job.
The problems in the high section of the runway became known after a strong earthquake shook the capital in 2017, according to the first diplomat.
Ebrard issued a statement Wednesday defending its role in the subway project, saying its office had held an international tender to select construction companies.
He also set up an autonomous public body to manage the project, as well as a central committee and a technical subcommittee, and sought advice from Mexican engineering institutes, he added.
Mexican billionaire Carlos Slim is also conducting investigations into the disaster since one of his companies was involved in the construction of the collapsed section.
Lopez Obrador reiterated Wednesday before the publication of the report that those responsible for the tragedy will be punished and promised to support the reconstruction of the line.
He rejected suggestions from a employers ’association that the accident was linked to public spending cuts.
Authorities were also under fire from one of the subway unions, which said its first alert about damage to the horse was ignored.
Line 12, also known as the Gold Line, was built at a cost of about $ 1.2 billion – 70 percent more than initially planned.
In 2014, operations were suspended at 12 stations along the line for just over a year due to runway deterioration, rail attachments and connections.