Levels of the blue-green algae in Taihu Lake have returned to normal and no longer pose a threat to the water supply for the city's 5.8 million residents, a local official and scientist said last Friday.

"Our latest monitoring and tests show the algae level in the lake is similar to the average over recent years," Hu Weiping, a researcher with the Nanjing institute of geography and lake science of the Chinese Academy of Sciences, said.

"The algae is quite normal in the lake at this time, and it is too much to call it an outbreak at these levels," Hu, whose institute has been monitoring Taihu Lake for two decades, said.

Earlier reports said satellite pictures of the lake showed it was covered in carpets of the blue-green algae. The reports raised public fears the city would once again suffer a loss of its water supply. An outbreak of algae at the end of last month led to the contamination of tap water across much of Wuxi, Jiangsu Province.

"After receiving the reports, environmental and meteorological officials from State, provincial and city levels immediately formed an inspection team to visit Taihu Lake. They found the situation was not as serious as the satellite pictures suggested," Yang Weize, Party secretary of Wuxi, said.

The city has also established six working mechanisms to ensure a safe water supply for local residents, Yang said. They include round-the-clock monitoring of water quality at the lake and closing factories and farms that cause pollution.

The Zhongqiao Water Plant, which produces 600,000 tons of tap water for the city every day, pours about 10 tons of active carbon into the water to filter floating waste.

"Unchecked tap water will not be allowed to flow out," Zhou Shengdong, head of the water quality examination center of the city's tap water company, said.

She said the company will guarantee the city's tap water quality by observing the new national water quality standard, which comes into force at the beginning of next month.