South Korean news agency Yonhap reported that the incident occurred at the P8 factory in Paju, about 40 kilometers north of Seoul, around 12:50 p.m. (0350 GMT) during routine maintenance work.
Yonhap quoted firefighters as saying that the valve of a nitrogen gas cylinder was presumably opened by mistake. Although Earth's atmosphere is nearly 80 percent Nitrogen, it can cause asphyxiation in the absence of oxygen.
Authorities said that one worker had died at the scene, while another was pronounced dead on his way to the hospital. One of the injured is in serious condition, added LG Display - South Korea's leading constructor of liquid crystal displays (LCD).
Soon after, LG Display offered its apologies in a statement
"We send our most heartfelt condolences and apologies to the deceased and will do everything in our power to help the injured recover as quickly as possible."
In Dec. 2014, a similar nitrogen leak occurred at the Shingori 3 nuclear reactor in Ulsan, some 410 kilometers southeast of Seoul.