Hanwha Aerospace explosion likely occurred while cleaning explosive waste: police

Deadly explosion at a Hanwha Aerospace facility is captured on a CCTV feed in this photo released June 24. Courtesy of DPK lawmaker Park Jung-hyun's office

Last month's deadly explosion at a Hanwha Aerospace facility in Daejeon appears to have occurred while cleaning a washing machine that may have contained explosive waste residue, police officials said Thursday.

The Daejeon Metropolitan Police Agency unveiled its initial assessment in a press briefing, citing a statement from a worker who was cleaning a tank within the washing machine at the time of the explosion on June 1 that left five workers killed and two others injured in the city located some 130 kilometers south of Seoul.

"I was cleaning a tank inside a washing machine at the time of the explosion. The blast seemed to originate from the machine," the worker was quoted as telling police.

According to the police, workers used chisel-like metallic scalers to remove waste residue accumulated on the washing machine, which, apparently, may have included explosive waste.

Investigators have secured 17 items from the scene, including tools believed to have been used to clean the machine, and requested a forensic analysis by the National Forensic Service, they said.

Still, the police said the suspected cause of the explosion remains only a possibility and that they are also considering other potential causes, such as electricity, impact or friction within the workplace.

The investigators have so far conducted three joint forensic examinations, seized and analyzed over 5,700 documents and items while questioning 32 individuals involved.

Authorities have booked Ga Jae-woong, head of the Daejeon plant, and Sohn Jae-il, the CEO of Hanwha Aerospace, over their alleged responsibilities in the explosion.