An orange toxic cloud hovers over the town of Igualada, near Barcelona, Spain. Alba Aribau / Reuters

An accident at a chemical distribution company near Barcelona on Feb. 12 injured three people and sent a giant orange cloud spreading through the skies over the surrounding towns. On a day with little wind, the cloud hovered over the towns like an alien presence in a science fiction film.

The accident occurred at 9:45 in the moning, when two chemicals were accidentally mixed together and exploded during delivery at the company, Simar. One of the two chemicals involved was nitric acid, which is corrosive and toxic. Officials warned residents to stay indoors to avoid the toxic cloud.

A few hours after the cloud appeared, officials lifted the ban on going outdoors.