The Seoul Metropolitan Government issued its first algae advisory in four years Thursday for some parts of the Han River that runs through the capital city, while some city residents were stocking up on bottled water, Yonhap News Agency reported.
Two consecutive tests on the water showed excessive concentrations of blue-green micro-organisms, leading authorities to advise people to drink tap water only after it has been boiled and cooled.
Some residents said they still weren't confident about using tap water.
"I and my husband used to drink some three big bottles of water in one week, but I bought two extra bottles this week out of fear the running water is ridden with toxic substances," 31-year-old housewife Kim Jae-yeon said. "I began using the bottled water not only for drinking but also for cooking and brushing teeth."
E-Mart, the country's leading retailer, reported sales of bottled water at its outlets nationwide increased 64 percent over the past week.