One worker died and six others were injured while cleaning a wastewater tank at a plant operated by Hyundai Steel in Incheon on Tuesday.

According to fire authorities and the police, seven employees collapsed during the cleaning work at around 11:02 a.m.

A 34-year-old worker, who was found in cardiac arrest, died after arriving at a nearby hospital, and the six others are receiving treatment for clouded consciousness and respiratory difficulty.

The workers, outsourced employees of a cleaning company, were removing sludge of hydrofluoric acid and nitric acid from the tank without gas masks.

While the police have launched an investigation, an official from the labor ministry's regional office said the government will look into applying the Serious Accidents Punishment Act against Hyundai Steel.