Joint investigation begins after third deadly blast at Hanwha Aerospace's Daejeon factory leaves 7 casualties

Police and fire authorities launched a joint forensic inspection Monday at the Hanwha Aerospace factory in Daejeon, where an explosion killed five workers and injured two others — the third deadly blast at the same site in less than a decade. Similar explosions at the facility in 2018 and 2019 killed five and three workers, respectively, prompting calls for a thorough investigation into root causes and fundamental safety reforms. Concerns have also emerged that the findings could affect the safety certification of the company's export products.

Police, fire investigators, the National Forensic Service and the Korea Occupational Safety and Health Agency began a detailed joint inspection at the scene at 10 a.m. Monday, with the goal of determining what triggered the explosion.

According to police and fire authorities, the blast and subsequent fire broke out at around 10:59 a.m. Sunday in the cleaning room of Building 56 at the Hanwha Aerospace factory in Oesamdong, Yuseong-gu, Daejeon. Hanwha said seven workers had been cleaning tools contaminated with propellant — an explosive compound — at the time of the accident.

About 20 minutes after the explosion, at around 11:17 a.m., fire authorities declared a Level 1 emergency response and deployed 33 pieces of equipment and 101 personnel to fight the blaze, which was brought under control roughly two hours later. Five workers died in the accident and two sustained serious injuries; one of the injured suffered severe burns across the body.

Eom Hyo-sik, head of the defense security division at the Korea Defense and Security Forum — who worked at Hanwha during the 2018 and 2019 accidents — said propellant is a sensitive material that can ignite even from static electricity. He added, however, that investigators should keep multiple possibilities open, including whether the explosion actually originated in the cleaning room or in an adjacent workspace.

The Daejeon Metropolitan Police Agency and the Daejeon District Prosecutors' Office each formed dedicated investigative teams to examine both the cause of the explosion and potential negligence by the company. The Ministry of Employment and Labor issued an immediate work-suspension order at the Hanwha Aerospace site and launched a probe into possible violations of the Occupational Safety and Health Act and the Serious Accidents Punishment Act.

The Daejeon factory has now been the site of three major explosions that have collectively claimed 13 lives. In May 2018, two workers died at the scene and three others who had sustained burns died during treatment. In February 2019, an explosion and fire in the propellant demolding room of Building 70 at the same factory killed three more workers.

Both earlier accidents were attributed to inadequate safety management. In the 2018 incident, investigators found that workers had struck the valve of a propellant container with a rubber mallet after the filling equipment malfunctioned. The 2019 explosion was caused by residual static electricity inside a rocket propellant unit reacting with the explosive material; it later emerged that a grounding device to discharge static electricity had not been installed.

The Ministry of Employment and Labor conducted special labor inspections and safety assessments following those accidents, but the recurrence of a fatal disaster seven years later is expected to put the factory's safety practices under intense scrutiny.

At a briefing Sunday, Hanwha said the cleaning room where the accident occurred had ordinarily been classified as a low-risk space. On safety equipment, the company said flame-retardant suits and blast barriers were installed in certain zones and that some areas were partially isolated, but added that the precise point of the explosion still required further confirmation.

Shin Jong-woo, secretary-general of the Korea Defense and Security Forum, called for a close examination of whether safety protocols had been strictly followed. "This is not a place that just started cleaning operations yesterday," he said, adding that a fire breaking out in the cleaning room was difficult to understand.

Kong Ha-seong, a professor of fire and disaster prevention at Woosuk University, said static electricity management is the cornerstone of safety in high-risk propellant processes. "Even a minute amount of static electricity can trigger a large-scale explosion," he said, and went on to say that static could be generated from unexpected sources such as the use of high-pressure water or friction from work clothing.

President Lee Jae-myung, speaking at a Cabinet meeting Monday, offered condolences to those who lost their lives and wished a swift recovery to the injured. "The relevant authorities must thoroughly investigate the cause of the accident and spare no effort in establishing measures to prevent a recurrence," he said. "Please also move quickly to conduct safety inspections at other similar facilities."

Lee particularly noted that "the repeated occurrence of the same type of accident at the same workplace is a serious problem" and directed the Ministry of Employment and Labor to identify such workplaces and report back to him separately.

Concerns have also been raised that the investigation's findings could disrupt future exports and deliveries. The Daejeon factory is understood to produce several weapons systems, including the Korea Tactical Surface-to-Surface Missile (KTSSM), the Chunmoo multiple rocket launcher, the long-range surface-to-air missile system L-SAM and the air defense missile system Cheongung-II.

Eom said the implications for export product safety would depend on which weapons system the propellant in question was destined for. "It will be necessary to get to the bottom of the cause and dispel the anxiety of countries that import these products," he said.

The two major umbrella labor federations each issued statements condemning the accident as a systemic failure of safety management and demanding severe punishment for those responsible and the introduction of concrete preventive measures.

The Korean Confederation of Trade Unions said officials indicted over the 2018 and 2019 explosions received suspended sentences, while Hanwha itself was fined only 50 million won (about $33,100). "Perfunctory, slap-on-the-wrist punishment has once again led to a serious industrial disaster and cost workers their lives," the federation said.

The Federation of Korean Trade Unions also issued a statement saying that the recurrence of a similar accident at the same workplace made a thorough review of the entire safety management and accident-prevention system unavoidable. "The government and the company must clearly establish the cause of the accident and fix responsibility," it said.