UPDATE: RESIDENTS have now been advised that air quality has returned to normal after the fire brigade brought in bulldozers to help extinguish the blaze.
RESIDENTS of three Madrid towns have been warned to stay indoors due to a poisonous magnesium cloud.
The announcement comes after flames ripped through a warehouse on the Fuenlabrada industrial estate, reducing 40 tonnes of magnesium and aluminium chips to ashes.
Citizens of Griñon, Humanes and Moraleja de Enmedio should not leave their homes until further notice, the 112 emergency service said in a statement.
Fire fighters have been unable to contain the blaze because burning magnesium can explode when exposed to water, leading them to use a special salt.
A 47-year-old man was hospitalised as the fire broke out, while the entire estate and a nearby hotel have been evacuated and the M-506 road closed to traffic.