A large metal plate launched by an explosion at a chemical plant in Spain's autonomous Catalonia region killed a man 3km (two miles) away.
The man, named only as Sergio, was in his apartment when the one tonne object struck, causing part of the building to collapse, officials have confirmed.
A factory employee was also killed in Tuesday's blast. Another worker died from injuries on Wednesday.
The explosion occurred at about 18:40 local time (17:40 GMT) in La Canonja.
Authorities said it was probably caused by a chemical accident, but that no toxic substances were released.
People were, however, initially urged to stay indoors when the explosion at the site just south of Tarragona set off a huge fire.
Residents of the Plaça García Lorca housing estate in nearby Torreforta, where the man was killed, described seeing "a ball of fire" stream across the sky at the time of the incident.
Firefighters later confirmed that this was a metal plate from the factory site, which they said weighed about a tonne.
Continuem la investigació de l’accident mortal d’ahir en un pis a Torreforta. La peça metàl·lica que hauria impactat a l’edifici faria aproximadament 122x165x3 cm #Plaseqcat pic.twitter.com/GUPDcwuKkV— Mossos (@mossos) January 15, 2020
Local resident Antonia Mora told Spanish newspaper El Pais "it was like a bomb".
Witnesses described seeing a large object hit the building, causing damage to the exterior.
Dozens of firefighters worked through the night and into Wednesday to tackle the blaze at the Industrias Químicas del Óxido de Etileno plant.
A reporter for Spanish public broadcaster RTVE, Jesús Navarro, tweeted an image showing a mangled structure at the factory site.
🔴 #ÚltimaHora #Urgente— Jesús Navarro (@JesusNavarro) January 14, 2020
Una persona ha fallecido tras un #derrumbe en un edificio de la plaza García Lorca del barrio de #Torreforta, en #Tarragona, por la onda expansiva que ha generado la #explosión, que de momento deja una persona #desaparecida y seis heridos. pic.twitter.com/mpWPXR6uY8
Water was sprayed over tanks containing chemicals to keep them cool.
The factory produces chemicals such as ethylene oxide - which can be used to make antifreeze, pesticides and to sterilise hospital equipment - and propylene oxide, which is used to make plastics. Both are extremely flammable.
Rescue teams with search dogs found the body of the second victim, a senior staff member at the factory, in the early hours of Wednesday. The search had been called off overnight due to poor visibility and dangerous conditions.
Eight people were injured in the explosion, and one of them died on Wednesday.
Late on Tuesday Catalan leader Quim Torra told reporters: "Now we can send a message of calm and confidence to people. There is no toxicity and therefore people can carry on with their lives as normal."
Spanish Prime Minister Pedro Sánchez later offered support to Catalan authorities in dealing with the accident.
Roads and public transport systems in the area that were closed as a precaution were reopened on Wednesday.