The police and the labor ministry conducted raids in connection to a petrochemical factory in the southwestern city of Yeosu, where an explosion last Friday killed four workers and injured four others.

Authorities began the search and seizure at three locations, including the field office of Yeochun NCC factory number three and that of the firm's subcontractor at around 9:00 a.m. Monday.

The operation will determine whether the company violated the newly enacted workplace disaster law aimed at better protecting workers from industrial accidents.

Meanwhile, forensic officials began autopsies of the four deceased workers to determine the exact cause of death. Related agencies are set to conduct a second round of on-site inspections starting at 2:00 p.m.

A labor ministry official said authorities are approaching the investigation with the utmost seriousness, especially as the company had reported a similar accident in 2018.

Police have booked the on-site chief official on charges of manslaughter due to professional negligence, while the labor ministry's regional office booked the factory manager for violating the Occupational Safety and Health Act.