The main gate of Hyundai Motor Company’s Ulsan plant photographed on Tuesday (Yonhap)

Three researchers died of suffocation during a vehicle testing at Hyundai Motor Company’s car manufacturing plant in Ulsan, some 300 kilometers southeast of Seoul.

According to police officials Tuesday, a man in his 40s, another in his 30s and one unidentified person were found unconscious at 3 p.m., following a vehicle test conducted in the multi-environment chamber within the plant's electrical quality division. The test involves vehicles being exposed to vibration as well as high temperatures and humidity.

“We extend our deepest condolences to the bereaved family. The company will promptly identify the cause of this accident and take all necessary actions (to investigate the accident.) We will also implement measures to prevent such tragedies,” said an official from Hyundai Motor Group.

“We are unable to provide further details about the incident, as it is currently under investigation by authorities, including the police and fire department,” the official added.