Authorities launch joint investigation after explosion kills five workers at Hanwha's key missile and propulsion facility Police officials enter the Hanwha Aerospace's Daejeon facility in Oesam-dong, Yuseong-gu, Tuesday to conduct a joint investigation into the explosion. (Yonhap) Hanwha Aerospace has halted part of its production operations at its Daejeon facility following a deadly explosion that killed five workers and injured two others, as authorities launch a joint investigation into the cause of the accident.The Hanwha Group defense affiliate said in a regulatory filing Tuesday that it suspended parts of production at its Daejeon site from Monday, after receiving a suspension order from the Daejeon Regional Employment and Labor Office.The company said the order was issued due to a “serious industrial accident” under the nation’s Occupational Safety and Health Act, which applies when at least one worker is killed.Operations will not resume until investigators determine the cause of the incident, mandatory safety training is completed across the facility and preventive measures are put in place. The timing of production resumption has not been decided, it said.An explosion and subsequent fire occurred on Monday at Hanwha Aerospace’s Daejeon plant in Yuseong-gu, a key facility involved in missile and rocket propulsion-related manufacturing. Authorities said five workers were killed and two others suffered serious and minor injuries.The company said the explosion may have occurred during a cleaning operation to remove explosive residue from tools used in the manufacturing process of rocket propellant. The exact cause is not yet known.The building where the blast occurred sustained partial damage, but it is not at risk of collapse, according to police.Police launched a joint investigation on Tuesday to determine the exact cause of the explosion. The inspection involved around 30 officials from the Daejeon Metropolitan Police Agency, the fire service, the National Forensic Service, the labor ministry and the Korea Occupational Safety and Health Agency. Bereaved family members also participated in the inspection, though police did not specify to what extent.The Defense Acquisition Program Administration said it has formed a dedicated task force to determine the cause of the accident and coordinate follow-up measures with the company and related government agencies.Separately, the labor ministry assembled an investigation team of more than 20 officials and launched a probe into the accident, including whether safety regulations were properly followed.President Lee Jae Myung on Tuesday called for a thorough investigation into the incident and swift measures to prevent similar accidents from recurring.Speaking during a cabinet meeting, Lee expressed condolences to the victims and wished a speedy recovery for those injured."It is a serious problem that the same type of accident continues to occur at the same workplace," Lee said, urging authorities to expedite safety inspections at other facilities handling similar materials and operations.The Korean Metal Workers' Union also called for a comprehensive investigation, and for those executives responsible for the explosion to be held accountable and punished under South Korea’s Serious Accident Punishment Act.“The company’s share price has been skyrocketing on the back of the ‘K-defense’ boom, but serious industrial accidents of a kind more often seen in less-developed countries are still occurring at its worksites,” said Jung Sang-man, vice president of the KMWU, at an emergency press conference held in front of Hanwha Group’s headquarters in Seoul. "Authorities should conduct a comprehensive investigation and strengthen penalties accordingly."The Daejeon facility is one of Hanwha Aerospace's key aerospace and defense research and production sites, and is designated as a national high-security defense industry facility.At the site, the company produces weapons systems, including the Chunmoo multiple launch rocket system, long-range surface-to-air missiles and the Cheongeom air-to-ground guided missiles. The facility also develops and produces large-scale propulsion systems and handles propellant mixing and loading operations.The affected production lines brought in 1.32 trillion won ($870 million) in revenue last year, representing roughly 4.94 percent of Hanwha Aerospace's total annual revenue of 26.7 trillion won.Industry officials expect at least some disruption to production and research and development operations at the facility, as cleaning of explosive residue from work tools is an indispensable step in the manufacturing process.