“Right now, we have three seriously injured by burns and other injuries,” a spokesman for the firefighters said, adding that 27 others were also hurt to a lesser degree.
He said authorities were probing the cause of the explosion in the warehouse in Arganda del Rey, some 30 kilometres (19 miles) southeast of the Spanish capital.
Madrid's 112 emergency services centre tweeted that there had been “several explosions.”
Incendio en planta industrial en Arganda del Rey. Vereda de las Yeguas. #BomberosCM y #SUMMA112 en el lugar. Varias explosiones. pic.twitter.com/kD6E7xAHDz
— 112 Comunidad Madrid (@112cmadrid) May 4, 2017
The Guardia Civil police force meanwhile posted a video of a large, black column of smoke billowing from the warehouse, and announced it was evacuating the zone, which includes several schools.
Tremenda explosión en Arganda pic.twitter.com/HxNoQ9ey7q
— Alejandro Varela (@varela_93) May 4, 2017
Firefighters were still working to extinguish the blaze.
It was not yet known whether the smoke was toxic, but the emergency services centre said an air quality measuring station in Arganda del Rey showed normal readings.
“A mobile unit is going to take measurements in the zone,” it added.
The Guardia Civil police force meanwhile posted a video of a large, black column of smoke billowing from the warehouse, and announced it was evacuating the zone, which includes several schools.
“Neighbours have been asked not to leave their homes and to keep windows closed,” a spokesman for Arganda del Rey's city hall told AFP, emphasising however that air quality was “normal”.
Requimsa, the company that owns the site, “manages and collects all types of hazardous waste”, according to its website.