Photo: The Canadian Press

An elevated section of the Mexico City metro collapsed and sent the train plunging toward a busy boulevard late Monday, killing at least 23 people and injuring at least 79, city officials said.

Rescuers found four bodies trapped inside a rail car that was dangling from the overpass but were unable to remove them. It was not clear if those dead were included among the 23. A crane was brought in Tuesday to lower the car down.

Mayor Claudia Sheinbaum said one of the concrete beams collapsed as a subway train passed over it in one of the deadliest episodes in the history of the city’s subway system, which is among the busiest in the world.

Mexican Foreign Relations Secretary Marcelo Ebrard called the collapse “the most terrible accident we have ever had in mass transportation.” Ebrard was Mexico City’s mayor from 2006 to 2012, when the line in question was built, and the collapse could represent a major blow for him.

“The cause of the collapse of the beam must be established through an expert investigation,” Sheinbaum said.

Earlier she said someone had been pulled alive from a car that was trapped on the road below. She said 77 of the injured were hospitalized. She also said children were among the dead.

Hundreds of police officers and firefighters cordoned off the scene overnight as desperate friends and relatives of people believed to be on the train gathered outside the security perimeter. Despite the fact that the coronavirus situation remains serious in Mexico City, they crowded together as they waited for news.

The collapse occurred on the newest of the Mexico City subway’s lines, Line 12, which stretches far into the city’s south side. Like many of the city’s dozen subway lines, it runs underground through more central areas of the city of 9 million, but then runs on elevated concrete structures on the city’s outskirts.

It was not clear whether a 7.1-magnitude earthquake in 2017 could have affected the subway line. There were reports that cracks had appeared in the base of at least one of the columns that support the elevated track following that quake.

The line was closed Tuesday, and hundreds of buses were called in.