This photo provided by Wonju Fire Station shows a tank at the plant of the Foosung Precision Industry Co. in Wonju, a city located about 130 kilometers east of Seoul, on Nov. 10, 2018. (Yonhap)
The accident took place at around 9:45 a.m., sending out plumes of black smoke from the plant of the Foosung Precision Industry Co., which makes fluoropolymer-lined tanks, pipes and valves.
This photo provided by Wonju Fire Station shows a tank at the plant of the Foosung Precision Industry Co. in Wonju, a city located about 130 kilometers east of Seoul, on Nov. 10, 2018. (Yonhap) This photo provided by Wonju Fire Station shows a tank at the plant of the Foosung Precision Industry Co. in Wonju, a city located about 130 kilometers east of Seoul, on Nov. 10, 2018. (Yonhap)
A 20-year-old worker suffered third-degree burns to his face, while a 32-year-old worker suffered second-degree burns to his legs and a broken left leg, a fire official said by phone from Wonju, a city located about 130 kilometers east of Seoul.
An official of the Wonju Severance Christian Hospital said treatment was underway for the two injured men but did not provide any further details on their medical status.
The two other workers -- both men in their 30s -- are presumed to have been killed inside a tank, and their bodies were taken to Wonju Medical Center, according to the fire official.
This photo provided by Wonju Fire Station shows a firefighter working near a tank at the plant of the Foosung Precision Industry Co. in Wonju, a city located about 130 kilometers east of Seoul, on Nov. 10, 2018. (Yonhap) This photo provided by Wonju Fire Station shows a firefighter working near a tank at the plant of the Foosung Precision Industry Co. in Wonju, a city located about 130 kilometers east of Seoul, on Nov. 10, 2018. (Yonhap)
The police said the blast appeared to have occurred after a fire broke out as the four Vietnamese were working to make a tank designed to carry a chemical needed in making semiconductors.
But fire officials said there was a blast but no fire.
It remains unclear why there are discrepancies.
The National Forensic Service and the Occupational Safety and Health Research Institute are set to conduct a joint probe on Monday to try to find the exact cause of the accident, a police officer said by phone from Wonju.
An official of the Foosung Precision Industry declined to give any details of the accident.
All officials spoke on condition of anonymity, citing policy.
The company said its fluoropolymer products are used in making semiconductors, petrochemical engineering, food processing, pharmacy, papermaking and metal treatment.
