HANOI (DPA) - A top government official confirmed on Tuesday (Oct 15) that tap water across south-east Hanoi is contaminated with styrene, a carcinogenic substance, state media reported.

Since last Thursday, residents in the Vietnamese capital have encountered polluted water supplies, with many reporting a smell similar to burning plastic coming from their tap water, and have thus turned to bottled water in frustration.

According to newspaper VnExpress, the smell appeared after an unidentified 2.5-tonne truck dumped oil into a branch of the Red River, a few hours' drive north-east of Hanoi, on Oct 8.

Viwasupco, the company in charge of processing water in the area, was reportedly aware of the problem yet had failed to alert officials and continued to supply water to Hanoi.

Hanoi officials say the company needs to take responsibility.

Mr Hoang Van Thuc, deputy head of the Vietnam Environment Administration, called the water pollution a "serious and irresponsible act of vandalism" that has affected thousands in Hanoi.

On Tuesday, Hanoi city chairman Nguyen Duc Chung confirmed in a meeting with Vietnamese President Nguyen Phu Trong that the company's water is contaminated, with tests showing styrene levels in the water to be nearly four times higher than normal in some areas.

Free water will now be supplied to those affected.

Styrene is an organic compound and flammable liquid used to create polystyrene, fibreglass, rubber and latex. The World Health Organisation states that acute exposure to styrene vapour causes irritation of the skin, eyes, respiratory tract and central nervous system, while evidence of carcinogenicity has also been observed.