A Vietnamese worker in his 30s was killed when a boxed polyurethane foam product exploded at a shipping terminal in Hwaseong, Gyeonggi Province, local police said Wednesday.

The incident occurred Monday, when the unnamed man whose main task is sorting packages was handling a box containing 15 cans of spray polyurethane foam. One of the cans exploded, striking the victim in his chest and causing the injury that eventually killed him.

Officials said while polyurethane foam can spontaneously ignite at high temperatures, they are unsure exactly what caused this particular explosion, as it occurred in only one of the 15 products. While looking into the possibility of a product defect, the investigators are also reviewing safety measures that had been implemented at the distribution hub.

Polyurethane foam is a material used mostly for thermal insulation, with its applications varying from furniture and packaging to automotive seating and more. The material is highly flammable, and can form toxic materials upon combustion, including extremely poisonous hydrogen cyanide.

In April 2020, a fire broke out at a shipping terminal of a local packaging company in Icheon, Gyeonggi Province, killing 38 and injuring 10. It was later found that the fire was caused by polyurethane foam and other flammable materials there ignited by a spark from a welding machine used in construction.

The incident sparked calls for safety and the previous administration moved to reinforce monitoring at construction sites, but the decision was reversed by the incumbent Yoon Suk Yeol administration, which viewed it as excessive regulation.