A simple helium balloon interrupted Madrid’s subway service on Line 2 for an hour on Wednesday morning.
In security footage, the metallic-surfaced balloon – which Metro de Madrid authorities said was being carried by a child – is seen floating around Sol station, then getting stuck on the overhead power cable and touching the top of an incoming train.
The combination created a “traction jump,” which has a similar effect to a fuse blowing. Sparks went off, burning the greased layer on the tracks and damaging cables.
As a result, service between Banco de España and Santo Domingo was suspended between 7.15am and 8.15am, during rush hour.
Metro authorities said that passengers inside Sol station were never in any danger.