Mexico will punish those responsible for an overpass collapse that killed at least 24 people and injured dozens when a train on Mexico City's newest metro line plunged onto a busy road below, the government says.
Accompanied by officials involved in the construction and maintenance of the elevated metro line that collapsed on Monday night, President Andres Manuel Lopez Obrador said the investigation should be done quickly and that nothing should be hidden from the public.
"There's no impunity for anyone," he told a news conference on Tuesday.
The crash has raised wider questions about safety on one of the world's busiest metro systems, which carries millions of people daily across the capital's urban sprawl.
Firefighters using heavy chains to stabilise the site pulled bodies and survivors from the wreckage before lowering one dangling carriage onto a truck in the afternoon. Some 79 people were injured, including three children, authorities said.
Video on social media showed the moment when the overpass suddenly plummeted onto a stream of cars near the Olivos station in the southeast of the city at around 10.30pm on Monday sending up clouds of dust and sparks.
Outside hospitals, family members grew frustrated waiting for information on relatives.
It was the second serious accident this year, after a fire at a central control building knocked out service on several lines for weeks following budget cuts.
The overpass that collapsed was part of Linea 12, an addition to the network finished less than a decade ago and long plagued by allegations of corruption and structural weakness.
In 2014, just two years after it opened, several of the line's stations were closed for structural repairs.
Investigations will be carried out by the federal attorney general's office, its Mexico City counterpart, and an external auditor, Norway's DNV GL, officials said.
US Vice President Kamala Harris and Canadian Prime Minister Justin Trudeau sent condolences to the families and friends of the victims of the accident and Lopez Obrador declared three days of national mourning.
A spokesman for Construction engineering company CCICSA did not immediately respond to a request for comment, but said in an earlier statement to Reuters the company stood in solidarity with victims' families and those injured.
"We are going to wait for the official expert opinion," CCICSA said.