Pesticide washed down from trees by rain was blamed for the death of around 1,000 fish at Beijing's Old Summer Palace over the weekend, an official with the park said on Tuesday.

Workers at the Old Summer Palace, also known as Yuanmingyuan Park, sprayed pesticide on willows along the riverbank on Thursday as part of their maintenance routine. However, an unexpected downpour early on Sunday washed the pesticide into the river, said Zong Tianliang, spokesman for the attraction in northwest Beijing.

The poisoned water flowed into a 100-meter-long shallow brook, where more than 1,000 young fry were seen floating on the surface.

Zong denied local media reports that around 10,000 fish died.

Most of the fish were six-mm carp and the largest fry weight about 400 grams, said Zong.

He said the incident was the result of an accident, adding the strength of the pesticide was rather high and the shallow water in the brook failed to dilute the poison content.

Workers had used the pesticide in the park for many years and this was the first accident concerning its use, said Chen Chunxu, head of the plant management team of the park.

Chen said lessons had been learnt and they would adjust the strength of the pesticide and increase supervision and maintenance.

Weather conditions would also be taken into consideration in the future, officials with the park's administration said.

The river area where the dead fish were found had been cleaned up by Sunday afternoon.

Yuanmingyuan, the royal garden built in the early 18th century and once known as "Versailles of the East", was first overrun by British and French infantry in 1860. What survived that attack was largely ravaged in 1900 by an invasion force of soldiers from eight foreign countries.

The park, built on the ruins of the former garden as a reminder of foreign aggression, was in the spotlight two years ago for putting membranes at the bottom of its lake to keep water from seeping out during drought periods. Yet the membranes were criticized of having killed lakebed wildlife and stopped the flow of groundwater and the top environment agency ordered park management to remove them.

In addition to the dead fish incident, a large area of pond lilies in the Houhai Lake area of downtown Beijing began to wither over the past four days, according to a report released by the Beijing News on Tuesday.

Some residents living around the old Imperial Lake area, which has turned into a hot tourists destination that boasts peaceful lakeside landscape and many trendy restaurants, pubs and boutiques, are concerned about the water quality of the lake.

Experts from the Beijing Hydraulic Research Institute, which planted the lilies, said no problem has been detected after water quality examination of the lake area, attributing the death of the lilies to the climate.

Workers in charge of maintaining the plants in the area also said the water seems normal. They had cut off the withered leaves and branches, expecting them to blossom again.

The accident has highlighted the city's ongoing environmental concerns ahead of next year's Olympic Games.

Beijing authorities are striving to improve the city's water and air quality to realize the promise of staging a "Green Olympics", but the challenge is tough.

The city faces grave water supply problems as four of its 21 reservoirs have dried up, according to a report released by the municipal environment protection bureau last year.

Meanwhile, nearly half of Beijing's sightseeing lakes and ponds are so polluted that their water cannot even be used to irrigate the park landscape that surrounds them.

The report said water quality in seven of Beijing's lakes, such as the Winter Palace Lake and Taoranting Lake, can be used only for irrigation. Only four lakes could be used to supply drinking water, while water from the other lakes is only fit for industrial use.

Beijing authorities are striving to improve the city's water and air quality to realize the promise of staging a "Green Olympics", but the challenge is tough.

The municipal government plans to invest 12.46 billion yuan (US$1.59 billion) by 2010 to curb worsening water pollution and guarantee clean water supplies.

All rivers and lakes within Beijing's sixth ring road are expected to be cleaned up before the Olympics, two years ahead of the target date, said Liu Peibin, deputy general engineer with the Beijing Water Authority.

The city has rebuilt or closed 2,000 waste water courses in the last four years. A large sewage treatment network is helping the city to purify waste water at a daily capacity of 2.48 million cubic meters. From August next year, more than 90 percent of the sewage in the city will be treated as five more plants are set to be put into operation.

The city with about 16 million population conducted a four-day experiment on August 17-20 to test whether pulling 1.3 million cars off its roads each day would prove effective in reducing air pollution during the Games.

Experts say pulling 1.3 million motor vehicles off the roads in Beijing each day can reduce exhaust emissions by 40 percent.

(Xinhua News Agency August 29, 2007)