Three workers died at a Hyundai car plant on Tuesday, the South Korean automaker told AFP, with local reports suggesting it was an accident during a vehicle performance test.

Along with its affiliate Kia, Hyundai is the world’s third-largest automaker, recording more than 4.2 million units in global sales in 2023.

“Three research workers have died at an Ulsan assembly line,” a Hyundai representative told AFP.

“We are trying to determine the cause of the incident,” the representative said, without giving any further details.

Hyundai’s Ulsan plant is 370 kilometres (229 miles) southeast of Seoul, and the assembly line there has been described by the company as the “world’s largest single automobile plant” with an export shipping dock.

According to South Korea’s Yonhap news agency, the incident occurred during a vehicle performance test inside a chamber.

Unventilated exhaust gases inside the chamber might have been responsible for the fatal accident, Yonhap said.

“The three — two Hyundai researchers and the other affiliated with a subcontractor — were found collapsed at a test chamber of the plant where they were conducting a car performance test,” Yonhap reported.

“They were taken to nearby hospitals but were pronounced dead,” it said.

“The victims were presumed to have been suffocated due to toxic gas in the enclosed space, and a police investigation is under way to find the exact cause of the accident.”

Hyundai and Kia together account for around 80 percent of all new vehicle sales in the South Korean domestic market, according to 2023 data.

One worker died at the same Hyundai Motor factory in Ulsan in 2023 after his head was caught in a heat treatment machine during an inspection, local media reported at the time.

Hyundai was forced to issue an apology and said they would “do our best to come up with follow-up measures” to prevent such incidents. (AFP)