The explosion happened at the Darkem paints factory, in the industrial area of Scarmagno, a town near the Piedmont city.
Witnesses reported hearing a series of four explosions before the factory went up in flames.
Nobody was inside the building. Seven firefighters were hospitalized with burns, with one suffering third-degree burns to his face, chest and hands, La Repubblica reported.
Three policemen suffered smoke inhalation, while another dislocated his shoulder. Three others in the area were injured slightly.
Schools in Scarmagno were closed on Tuesday amid concerns over the environmental impact of the explosion, the cause of which is yet to be ascertained.