At least 15 people were killed and dozens injured when an elevated metro line collapsed in the Mexican capital on Monday as a train was passing, authorities said.

Security camera footage broadcast by local media showed the carriages plunging towards the ground in the south of the city.

"So far we have 15 people who unfortunately lost their lives," Mexico City Mayor Claudia Sheinbaum told reporters.

The Mexico City elevated metro line collapsed as a train was passing
The Mexico City elevated metro line collapsed as a train was passing AFP / Pedro PARDO

The city's civil defense department said on Twitter that around 70 others were injured in the dramatic accident.

Emergency services were seen working to rescue victims from the carriages at the Olivos station.