The blast at the factory south of the port city of Tarragona was probably the result of a chemical accident, Catalonia's civil defence agency said.
The explosion happened at 6.40pm local time, Efe news agency reports.
The explosion led to a fire, the regional service said, while fire departments sent 10 brigades to the area.
An enormous explosion at a petrochemical plant in northeastern Spain has killed one person and injured at least eight others, according to authorities.
A huge explosion at a chemical factory in Spain claimed the life of a person and injured eight others as authorities asked the residents to stay indoors.
Morlanes said the company was investigating the causes of the explosion but its inspectors could not approach the site while firefighters were still working.
The cause of the blast last night at the IQOXE facility - which specialises in the production of ethylene oxide, glycol and propylene oxide - is not immediately known.
The factory began operations in June 2017 and had been operating normally, he added, prior to Tuesday's explosion of a 20-tonne tank full of ethylene oxide. Fire chief Albert Ventosa said the blaze was under control.
Video footage showed high flames and columns of smoke around the complex.
Tarragona is located 71 miles southwest of Barcelona, the regional capital of Spain's Catalonia region.
The victim, named only as Sergio, died in his home in Torreforta, in Catalonia, Spain, when the one-tonne shrapnel collapsed his building on Tuesday, authorities said. I looked out to the window and I saw the flames. "I though I was going to have a heart attack".
Since 2015, the city has housed a 1200-hectare "chemical hub, " ChemMed, that was described as the largest of its kind in southern Europe.