The accident occurred at around 10 a.m. local time (01:00 GMT) at Hanwha chemical factory, affecting six workers at the scene and seven outside the building, the Yonhap news agency reported.
READ MORE: Number of Hospitalized Schoolchildren After Delhi Gas Leak Grows up to 310
The workers reportedly showed several symptoms of intoxication, including breathing difficulties, nausea, runny nose and others.
The police are investigating the causes of the incident but believe that the leak could have happened while chlorine was being transferred from a tanker truck to a storage tank.