A customer service agent said Friday that the closed stores are located in Cau Giay, Ha Dong and Nam Tu Liem districts, all of which use water that comes from the Da River in Hoa Binh Province. No reopening date has been set.

Other major coffee chains in the southwestern districts of Hanoi have remained open, with their managers saying, without elaborating, that they are getting clean water from a supplier.

Like Starbucks, many restaurants and eateries in Hanoi are struggling to get clean water.

Nghia, owner of a pho noodle stall in Hoang Mai District, said that he has spent hundreds of thousands of dong (VND100,000 = $4.3) on bottled water this week because the tap water smelled bad and could not be used for cooking.

A buffalo-meat restaurant chain with outlets in affected areas mobilize staff to work till midnight Wednesday to stock bottled water.

In some areas, bottled water prices have increased 2-3 times due to high demand. The Vietnam Directorate of Market Surveillance has asked Hanoi authorities to stop merchants from overpricing bottled water.

On Tuesday last week, a 2.5 ton truck was seen dumping used oil into a mountain creek in Phu Minh Commune, Hoa Binh Province. The oil spread and contaminated the tap water for about one million Hanoi residents.

Tests of the smelly water by authorities later found that the level of styrene, an organic compound that is classified as "probably" carcinogenic, was 1.3-3.6 times higher than normal.

On Thursday, Hanoi officials said the tap water samples collected Monday this year passed safety tests, but continued to advise against drinking or cooking with it.