What We Know About the Mexico City Train Crash

Follow live updates on the train crash in Mexico City.

A subway overpass collapsed on Monday night in Mexico City, sending the cars of a passenger train plunging to the ground and killing at least 23 people, including children, the city’s mayor said.At least 70 others were injured.

Here’s what we know about what happened:

A rail overpass collapsed.

At about 10:25 p.m., a crash occurred on Line 12 of the subway system in southeast Mexico City, between the Olivos and Tezonco stations.

Claudia Sheinbaum, Mexico City’s mayor, said a support beam on the overpass had collapsed as the train went by, The Associated Press reported. “At this moment, we can’t speculate about what happened,” she said. “There has to be a deep investigation, and whoever is responsible has be held responsible.”

Photos and videos of the crash released by the government showed at least one orange-and-yellow subway car hanging from an overpass. An eight-second video that captured the collapse showed automobile traffic flowing on either side of the suspended bridge. Suddenly, it cracks and buckles in a burst of concrete and sparks, falling between the lanes of vehicles.

Rescuers rushed to the scene.

As dawn approached, a crane was holding one car in the air as emergency workers checked to see if any passengers remained trapped.

Carlos Zúñiga Pérez, a television host in Mexico City, tweeted a video of emergency medical workers rescuing injured passengers from a tilted subway car by helping them down from ladders.

Mexico City Metro, officially called Sistema de Transporte Colectivo, warned residents to avoid the area. Ms. Sheinbaum said she was at the site supporting rescue personnel and that minors were among the dead. At least 70 people were injured, and 49 had been transferred to hospitals with injuries, she said.

Enrique Bonilla, 57, a passenger on the train, told the television network Televisa that people had fallen on top of one another and that he was able to grab onto a pole and escape through a broken window.

It was all over in seconds, Mr. Bonilla added. “Thank God I came out alive.”

Mexico City’s subway has faced problems.

The subway system in Mexico City, the country’s sprawling capital, handles more than four million passengers a day. It is the second-largest in the Americas, after the one in New York City.

When the system was inaugurated in 1969, it was the pride of Mexico, but in recent years it has become a symbol of urban decay.

There was concern over the integrity of the elevated tracks and support columns on the stretch of tracks where Monday’s accident occurred after a powerful earthquake hit Mexico in September 2017.

The elevated infrastructure on the subway line — known as Line 12, or the Golden Line — was damaged, El Universal newspaper reported.

Later that month, some local residents told El Universal that they feared that the damaged infrastructure might collapse. The newspaper reported at the time that a column between the Olivos and Nopalera stations had suffered structural damage.

It was not immediately clear what work had been done to address the safety concerns. The Golden Line, where Monday’s accident occurred, was opened in 2012 and is the newest in the system. Yet from the outset, it has faced problems, including the temporary suspension of service on a large part of it just 17 months after the line was inaugurated.

Follow live updates on the train crash in Mexico City.