Mexican authorities have promised a full investigation into the collapse of a metro overpass in Mexico City, as questions mount over the line's safety.President Andrés Manuel López Obrador said "nothing would be hidden" while the mayor said an external company would be involved in the inquiry.The elevated track on Line 12 fell on to a road, killing at least 24 people.Concerns over possible structural failures had been raised since the line was inaugurated, in 2012.There were concerns about design problems and construction standards, as well as allegations of corruption.At a news conference, President López Obrador said the investigation, to be carried out by federal and Mexico City prosecutors, should be done quickly. "We cannot get into speculation, much less blame the possible perpetrators without having proof," he said.
Mexico City's metro system is one of the most used in the world, carrying tens of millions of passengers a week. In North America, only New York's subway carries more people every day.Yet the incident did not occur on one of the older lines, which have been through at least two major earthquakes in the past 35 years. Rather it happened on Line 12, completed as recently as October 2012.There will be difficult questions for the mayor's office to come about the construction of the line, including for several former mayors.