SEOUL • Four workers were killed and two others were missing when a waste-water storage tank exploded yesterday at a chemical plant in the South Korean industrial city of Ulsan, the authorities said.
The blast at Hanwha Chemical occurred when the workers were doing welding work on the tank, said a spokesman for the Ulsan Nam Fire Station .
"Gas from the waste water, which had accumulated inside the tank, was apparently ignited by the welding torch," he said.
The plant makes polyvinyl chloride, which is used in products such as cling film, said the BBC.
An investigation is under way to determine whether the accident was a result of negligence, said the spokesman.