LG Display reported a leakage of nitrogen gas at its manufacturing plant in Paju, Gyeonggi Province, around 12:50 p.m. on Monday, which claimed two lives at the assembly lines.
The victims are two employees in their 30s, surnamed Moon and Lee, according to investigative authorities.
In addition, the factory near the western inter-Korean border reported that four other employees had been injured in the accident, all of whom were immediately taken to a hospital.
An LG Display official said it was likely the nitrogen gas had leaked from an assembly line for monitor panels during the cleaning process: "Various materials are used together with the nitrogen during the cleansing."
The Gyeonggi District Police Agency dispatched a group of forensic investigators to the factory.
Police said they were looking into whether the company conducted safety checks and the cause of the gas leak.
The accident came less than one month after similar leaks were reported from the state-controlled Korea Hydro and Nuclear Power Corp. In late December 2014, three workers were killed after inhaling nitrogen gas that leaked from a valve in the basement of the reactor operator.
Similar incidents occurred in 2013 at Hyundai Motor Group's manufacturing unit Hyundai Steel and those of its subcontractor Hyundai Greenpower.