Three people were injured in an explosion at chemical distributor Simar at Igualada, near Barcelona, Spain on Feb. 12.

Due to the blast, thousands of people were forced to stay indoors as a large toxic cloud spread over the area, the news agency Reuters reported.

The regional government of Catalonia said the blast appeared to have been caused by two chemicals coming into contact with each other during delivery to the plant, owned by Spanish company Simar.

Authorities said one of the chemicals, nitric acid -the only one to be named - is corrosive.

Reports said that following the explosion, a thick orange cloud could be seen emanating from the site in Igualada, some 60 km from Barcelona and then spread over residential areas nearby.

Traffic on some roads in the area and a train line were closed as precaution.