Three workers were found dead after an explosion took place at a chemical factory in the South Korean city of Yeosu on Monday, firefighters said.Fire broke out at 1.37 p.m. at a petrochemical manufacturing factory in the Yeosu Industrial Complex in Yeosu, 450 km south of Seoul, reports Yonhap News Agency.While a total of seven people were working at a chemicals storage facility of the factory, three of them were found dead at a nearby plant, apparently due to the strong impact of the explosion.The four others were confirmed to be safe, according to authorities.Authorities have issued a level-2 warning, which enables them to call in support, including firefighters, from other areas.But the call had been lifted as of 5.11 p.m. (local time), as firefighters had put out the fire completely.Authorities said they are now looking into the exact causes of the accident.