After nearly a week of boiling their tap water amid an E.coli scare, thousands of Copenhagen residents have been given the green light by city officials to resume normal use.

"This is the good news of the day. I am happy to say that everyone in the city now has access to clean drinking water," Lord Mayor Frank Jensen said in a statement late Wednesday.

Copenhagen Energy, which provides drinking water to the Danish capital, discovered unusually high levels of E.coli bacteria in the municipal tap water system last Friday.

The majority of Copenhagen's more than one million residents were advised to boil their water for at least two minutes before drinking it, but the advisory was limited to a smaller area of about 40,000 people in the city centre a day later after the source of the pollution was found: rainwater seeping into drinking water supplies in a construction area.

Copenhagen Energy said tests showed the water was again clean and safe to drink.