Mexico City metro: Fears structural failure behind deadly crash

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.

The line was built when Foreign Minister Marcelo Ebrard, a close ally of the president, was mayor of the capital. Speaking alongside the president, Mr Ebrard said it was a "very sad day for everyone".

Current Mayor Claudia Sheinbaum also said it was too soon to say who was responsible for what happened. Earlier, she said it appeared a girder had given way on the overpass. The line will remain closed while a structural survey is carried out.