No warning signs before blast that killed 5 at Hanwha Aerospace plant, probe finds

The explosion at Hanwha Aerospace's Daejeon plant that killed five people and injured two occurred without any warning signs, an investigation has found.

A fire department accident investigation report submitted to the office of Democratic Party of Korea lawmaker Park Jeong-hyeon included CCTV footage stills captured from outside Building 56's washing room at the time of the blast, according to Yonhap News Agency.

The images show flashes and flames bursting out of the building. Based on the footage, fire authorities concluded that the explosion occurred suddenly, with no preceding signs such as smoke or fire, and that flames spread afterward.

The accident took place at around 10:59 a.m. on June 1 inside Building 56 at the Hanwha Aerospace plant in Oesamdong, Yuseong-gu, Daejeon, while workers were conducting a washing operation. The facility is used to clean residual propellant — the explosive material used in missile and rocket production — from tools and equipment.

Fire authorities believe the explosion originated in "Separation Washing Room No. 1" at the center of Building 56. The cleaning process involved scraping equipment with a spatula-shaped tool, submerging it in a water tank, and then applying additional high-pressure washing.

The fire agency concluded that the propellant caused the explosion but has yet to identify the specific ignition source. A cleaning solvent initially flagged as a potential hazard due to its flammability was determined to be a non-hazardous material in tests conducted by both the Korea Fire Institute and the National Fire Research Institute.

Meanwhile, the government has launched a comprehensive joint inspection of all facilities nationwide that handle military explosives. Hanwha Aerospace has begun a full overhaul of its safety systems through an independent body led by outside experts.

The company plans to spend 452.4 billion won ($294 million) this year on safety and environmental improvements.