Samsung has confirmed that highly poisonous hydrofluoric acid gas has leaked at its main chip plant in the city of Hwaseong, South Korea. The incident comes a little more than three months after an earlier gas leak left one worker dead and four others injured. In a statement to Engadget, the company confirmed that three external contract workers were partially exposed to diluted hydrofluoric acid at Samsung’s main semiconductor facility. The incident occurred as workers were “upgrading parts of an existing facility in line with Ministry of Employment and Labor requirements.” Samsung said that it has reported the incident to the proper authorities and will work with investigators to find the source of the leak. All three workers were admitted to the hospital for further examination.