According to the Yonhap News Agency, firefighters have started a rescue operation in an attempt to find people who could have been trapped under the debris.
A spokeswoman at Gangwon Fire Headquarters has told the media outlet that the storage tank was used by a venture firm at the Gangwon Technopark in Gangneung, about 220 kilometres (135 miles) east of Seoul.
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At the moment, there is no official information about the possible causes behind the deadly explosion.