South Korean authorities have ordered workers to halt work at one of the naphtha crackers at the petrochemical company Yeochun NCC (YNCC) in the city of Yeosu, the country's emergency services said Friday, as an explosion at the petrochemical plant killed four and injured four others.

The incident at YNCC's third plant in Yeosu comes as businesses brace for greater scrutiny under a new South Korean law punishing management for incidents involving worker death.

The regional office of South Korea's labor ministry told Reuters that the ministry ordered workers to halt work at the entire third plant.

"There is no disruption in production, but we have entirely halted maintenance and repair work," an official at YNCC told Reuters.

YNCC's first and second plants are also operating, the YNCC official said, adding that the blast occurred during a leak test in a cleaning process that is a procedural operation carried out every four years. Its third naphtha cracker in Yeosu, the site of the explosion, produces 470,000 tons per year (tpy) of ethylene.

YNCC's first and second naphtha crackers in Yeosu produce 900,000 tpy and about 920,000 tpy of ethylene each.

The company's entire capacity is 2.29 million tpy, about 1.1% of global capacity, Samsung Securities analyst Cho Hyun-ryul said.

"If the impact is limited to the incident site, supply disruption will not be significant," he said.

"However, a suspension order for the entire production cannot be ruled out, as stricter rules are imposed on work sites since ... the Severe Accident Punishment Act. If so, this could affect not just 470,000 but 2.29 million tons."

The new South Korean law, which took effect late last month, imposes criminal punishment of one or more years of jail or fines up to 1 billion won ($834,028) for severe industrial accidents on business owners and responsible management, if they violated a duty of safety measures stipulated in the law.