Three researchers at Hyundai Motor’s Ulsan plant died of asphyxiation while conducting vehicle testing work on Tuesday. 

According to the police and industry observers, the three researchers were found unconscious by another plant worker around 3 p.m. in a chamber used to test vehicle performance. 

The three were transported to the hospital but were pronounced dead.

They are believed to have suffered asphyxiation while working in the chamber, which is big enough to fit a single vehicle. 

Industry observers believe the deaths occurred after exhaust fumes from the vehicle filled the chamber.

Two of the deceased were researchers at Hyundai Motor, and the third worked for a partner company.