Ulsan: Three researchers died of suffocation while testing vehicles at a Hyundai Motors plant in South Korea's southeastern city of Ulsan on Tuesday, prompting authorities to launch an investigation. The three were found unconscious in a test chamber where they were conducting a car performance test. According to Anadolu Agency, two of the victims were Hyundai researchers, while the third was associated with a subcontractor. They were transported to nearby hospitals, but doctors pronounced them dead. The victims were believed to have been suffocated by toxic gas in the enclosed space. Nonetheless, a police investigation is underway to determine the exact cause of the accident. The Labor Ministry is looking into the cause of the accident and reviewing the applicability of the 'Serious Accidents Punishment Act.' The act punishes business owners or responsible executives with at least one year in prison or a fine of up to one billion won (approximately $717,360) for severe industrial accidents that result in d eath or serious injury. Expressing condolences to the bereaved families, the automaker promised to "actively" take the necessary precautions to prevent a reoccurrence.