HEFEI, June 9 (Xinhua) -- Blue-green algae has extended five square kilometers in an eastern Chinese lake but does not threaten drinking water supplies, experts and officials in Anhui Province said.

    Environmental experts and officials are closely monitoring the potentially harmful algae bloom in Chaohu Lake, China's fifth largest freshwater lake, for signs of a massive bloom in the hot and arid weather.

    The local waterworks takes samples of the water for lab test once every two hours to ensure safety.

    So far, the local government is confident that drinking water is not threatened and the city is ready to divert Yangtze water to make up for supply in case the situation deteriorates.

    Though blue-green algae is found sparsely in an area of 40 square kilometers in the western part of Chaohu Lake, satellite pictures taken by the provincial meteorological institute shows just one bloom belt stretching about five kilometers long and one kilometer wide, said Zhang Zhiyuan, an official with the provincial environment protection bureau.

    He said water in Chaohu, a city of 320,000 on the lake's eastern banks, still meets the country's drinking water standards because it relies on the largely unpolluted eastern side of the lake for water supply.

    "In case the algae bloom spreads quickly and taint the eastern side of the lake, too, the city can still get an inflow of Yangtze River water at 200 cubic meters per second to ensure safe drinking water," he said.

    The algae bloom has not affected water supply in the provincial capital Hefei, which is 70 kilometers from Chaohu, because Hefei fetches water from two large reservoirs on its outskirts, said Zhang.

    Xinhua reporters smelt a fishy, rather than fetid, smell on the western banks of the lake on Saturday. Chaohu Lake literally means "Bird's Nest Lake" because its shape resembles a bird's nest. It is about 150 kilometers from Nanjing.

    A woman who's been working for years at a waterside restaurant said the algae along the banks was actually "thinner" than the previous years. And a speed boat runner gave a nod.

    "The lake water is apparently clearer this year than before," said Lu Zaiping, who offers tourists rides in his speedboat.

    Xiao Pu, a local environment official in Chaohu, said the lake suffers algae bloom every June and July and he saw no sign of deterioration this year.

    But Zhang Zhiyuan warns there could still be chances for massive algae bloom in Chaohu Lake, which has suffered high levels of nitrogen and phosphorus for years. "It's not possible to eradicate all the algae anytime soon."

    Chaohu Lake experienced a massive blue-green algae bloom in July 2004, but timely wind and rain helped it subside soon.

    Reports of the algae bloom on Chaohu Lake came amid widespread concerns over water safety in Wuxi, another eastern Chinese city, where the fast-spreading bloom that smothered Taihu Lake forced residents to buy bottled water in a panic last week.

    An inflow of Yangtze water has helped dilute the lake and by Saturday, authorities in Wuxi are still watching out for a comeback of the pollution belt as the high temperature hits 31 degrees Celsius.