(CNN) It's known as the "Golden Line." The Mexico City subway system Line 12, spanning 25.1 kilometers (15.6 miles) and featuring 20 stations, was touted as one of the most expensive and ambitious public works projects in Mexican history when it was inaugurated in October 2012.
"It reflects a technological advancement and state-of-the-art features that can only be compared to the construction of the great metro systems of the world," a Mexico City government official boasted during the kickoff ceremony.
The highly publicized ribbon-cutting was attended by the who's-who of Mexican politics and power at the time, including then-president Felipe Calderón and Marcelo Ebrard, who was then in his last days as Mexico City's mayor and is now foreign minister. Carlos Slim, Mexico's richest man and owner of one of the construction companies involved, was also there.
But fast forward eight years and the Golden Line is, in many respects, a symbol of Mexico's social ills and challenges from corruption to impunity, inequality to negligence -- especially after last week's deadly elevated rail collapse killed at least 26 people, making headlines around the world.
The Golden Line was supposed to connect historically marginalized neighborhoods with more prosperous areas of the Mexican metropolis and give people equal access to jobs, cultural centers and some of the best things Mexico City has to offer in an affordable way.
But several experts who spoke with CNN in the days following the collapse say this was a tragedy foretold.
Jorge Gaviño Ambriz, who served as Mexico City's Metro Director between 2015 and 2018, said he believes the collapse could have been avoided, though he would like to see first what kind of maintenance and inspection was done throughout the line.
"Evidently, it could've been avoided with proper maintenance," said Gaviño Ambriz. "I believe that if there are already photos from 2020 taken by some neighbors and showing the stretch that collapsed was already getting curved, a beam that curved down like a bow. If this doesn't get fixed, immediately an accident can happen," Gaviño Ambriz said.
Mexico City officials said at a press conference the day after the accident that the last structural inspection was done in January 2020 and showed no irregularities.
Sergio Alcocer, a structural engineer and researcher at the National Autonomous University of Mexico's Engineering School, said it is impossible to tell at first sight what caused the accident, even if there were cracks in the walls or bent beams.
"What happened with this structure is that there have been indeed some deficiencies in other stretches and we may want to extrapolate what happened with those stretches with what happened with the one that failed. There was indeed damage to a column that had to be repaired in 2017," Alcocer said. "Some have inferred that the damage resulting from the September 19, 2017 earthquake caused the collapse. I don't think so, but the investigators will have to look into that."
Commuters told CNN that over the years they had seen signs -- an uneven wall, a crack, service interruptions -- that made them wonder about its safety. The dozens of deaths and injuries caused by the collapse was the culmination of a long series of red-flag incidents that should have prompted authorities to suspend service or shut down the line completely, they say.
Outrage over the collapse has led to calls for current Metro Director Florencia Serranía to resign. The day after the collapse, she told the press she would not resign, but vowed to cooperate with any government and independent investigations.
Her agency will "submit to the attorney general's office all information in our possession so that the cause of this accident can be found," Serranía said last week. "Just like all the riders, we want to know the truth about what happened and we will cooperate with the authorities to that end."
In fact, the Golden Line had already been shut down or suspended service multiple times due to safety and operational concerns, sometimes leaving the estimated 385,000 passengers who depend on the service with limited alternatives. The two main disruptions in service happened in 2013 (only a year after opening) and for a long stretch between 2014 and 2015.
In October 2013, service was suspended on late nights and weekends at six of its 20 stations, due to what Mexico City's Metro Authority described as overnight and weekend maintenance to the tracks. And then, for a period of 20 months, from March 2014 to November 2015, the Golden Line was shut down in 11 stations due to structural concerns.
Transit system authorities concluded that it was "not possible to keep the elevated portions of Line 12 in operation until an exhaustive review is completed and we make the corrections and major maintenance work that will be needed," then-Metro Director Joel Ortega said at the time.
Upon reopening, then-Mexico City Mayor Miguel Angel Mancera vowed the line would never shut down again. "What we have now as opposed to what we had before is that maintenance will be guaranteed; I mean, we're guaranteeing that there can't be a shutdown because the companies we're working with are making sure this doesn't happen again," Mancera said.
Just after the March 2014 shutdown, The Mexican Institute for Competitiveness, a nonpartisan Mexican think tank, called Line 12 "a spectacular fiasco," not only because of its high cost, but also because of the apparent inability of the Mexico City authorities and the federal government to get things done right and within budget.
Icela Lagunas, an independent journalist who has covered the Line 12 issues for years, told CNN there were structural questions from the beginning about the type of trains and rail system that would be appropriate for the notoriously unstable ground in vast sectors of Mexico City, a metropolis that has been plagued by earthquakes. In September 2017, nearly 400 people died in central Mexico, including more than 200 in Mexico City, after a 7.1 magnitude earthquake rocked the area.
"This week's tragedy is a combination of many factors. It's a combination of corrupt officials, dismissing warnings and of a badly executed project that had mistakes since its inception," Lagunas said.
Ebrard, now Mexico's Foreign Minister under President Andrés Manuel López Obrador, reacted to the tragedy hours after the collapse. "What happened today [Monday] with the Metro is a terrible tragedy. My solidarity for the victims and their families. Of course, the cause must be investigated and justice sought. I reiterate that I'm at the disposal of authorities to assist as necessary," Ebrard wrote on his official Twitter account.
The following morning, during the president's daily morning press conference, Ebrard said he would cooperate with authorities. "This project was finalized with the approval of the following administration in July 2013. We could argue a lot about that. They reviewed everything for seven months. The final completion was achieved in July 2013. Moreover, I would like to say that he who acts with integrity fears nothing. He who owes nothing fears nothing," the foreign minister said.
Ebrard continued: "Like everybody, and especially as a high-level official and somebody who promoted the construction of the line, I'm subject to whatever authorities determine based on the investigation and their findings about who's responsible."
President Andrés Manuel López Obrador, who has been criticized by some for showing little empathy to victims and issuing warnings about using the tragedy for political gain, promised Wednesday his government will seek justice. "A thorough investigation will be conducted to punish those responsible. To that end, we have already established communication with a team of experts that will be in charge of this investigation and will issue an opinion so that we know the causes," the president said.
Current Mexico City Mayor Claudia Sheinbaum announced that, in addition to an investigation by the local attorney's office, Norwegian firm DNV will conduct an independent investigation.
Alejandro Hope, a Mexican columnist, told CNN that Line 12 "has been plagued by controversy from day one. It has been a project that was grossly over budget, about 70 percent of the original projected amount. It was also plagued by corruption allegations."
He also points out that there have been three major accidents in 14 months, including a train collision, a fire in a command center and the Monday Line 12 collapse.
"One incident is a coincidence, two incidents are bad luck, but when you talk about three you can say that this is already a pattern that has to be investigated," Hope said.
Enrique Bonilla, a Mexico City resident who says he frequently used Line 12, is one of the collapse survivors. He says he always suspected there was something wrong with it. "It would make very weird noises," Bonilla said. But he says he kept on using it because, like many people in his neighborhood, it made his commute significantly faster, easier and affordable.
He was able to return to his family hours after the accident. Other than some neck pain and a minor left arm injury, he says he's physically fine. His emotional well-being, Bonilla said, is an entirely different matter.
"I have been born again," he said, choking back tears. "I still can't figure out why I'm still here and others aren't. I get very emotional about it. I just want to forget."