SYDNEY, Australia (AP) _ Sydney's water system, flushed of deadly parasites, was declared safe for drinking Tuesday _ but residents' fears were not washed away so easily.

Health officials said the water treatment plant that spread the potentially deadly parasites, giardia and cryptosporidium, has been cleaned up and the city's water system flushed with clean water.

``We are absolutely clear that the water is safe to drink,'' said New South Wales chief health officer Andrew Wilson.

An outbreak of the microscopic parasites was found in the system July 30, forcing the city's 3.7 million residents to boil water or buy it bottled.

The health department said there had been no reported cases of illness from water contamination, but the parasites have an incubation period of a week or more.

Wilson said health officials would monitor reports of illness for the next two weeks.

But the fear and anger of Sydney residents promised to last longer than that.

Australian Consumers Association spokeswoman Mara Bun said she would not be surprised if people did not immediately return to drinking or using tap water.

``Consumers will have to buy unnecessary water filters and bottled water and the regulators will have to demonstrate that they have regained our trust,'' she said.

Sydney Water board chairman David Hill announced a $21 million upgrade of the city's water supply. He said the money will help pay for improved water storage controls and daily monitoring of water filtration outlets.

``They are extensive measures,'' Hill said. ``It is as much as we possibly could do to ensure that we don't see cryptosporidium and giardia in drinking water in the future.''

The parasites are most dangerous to people who already have weakened immune systems, including those suffering from AIDS.

Cryptosporidium got into the water supply of Milwaukee in 1993, contributing to the deaths of about 100 people. More than 400,000 others became ill.