Mexico City’s metro service reported at least 31 people were treated after smoke filled carriages in the Line 1 tunnels.

The smoke was reportedly caused by a failure of one of the trains on the network and smoke was reported at the Chapultepec and Juanacatlán stations.

At least 10 people were taken to hospital for further treatment, among them a pregnant woman, according to local reports.

This video shows the smoke in the tunnels from the platform of one of the affected stations. People emerging from the tunnel can be seen climbing onto the platform. Credit: Twitter/armand_alf88 via Storyful