Last night as Suen, 67, remained in hospital being treated for the disease, officials said samples were now being taken from water pipes on the 10th to 15th floors of the east wing which connect to pipes on the 11th floor.

However, the officials said that samples taken from the water tank that supplies the building had been given the all-clear.

The block at the centre of the health scare is home to the offices of seven government departments, including the Constitutional and Mainland Affairs Bureau, the Education Bureau, the Environment Bureau and the Security Bureau. Centre for Health Protection controller Dr Thomas Tsang Ho-fai said preliminary results from samples taken on December 22 showed Legionella pneumophila bacteria were found in four samples taken from the tap in the private toilet of Suen's office.

The investigation would focus on finding the spot in the pipes connecting Suen's toilet and the main tank where the growth of the bacteria may have taken place, said Tsang.

He added that the disease was not inter-personally transmitted and was usually contracted through inhaling contaminated water droplets.

It is a type of pneumonia that is caused by legionella, a type of bacteria found primarily in warm-water environments.

Tsang emphasised that the test results were only preliminary and it would take at least a few days for the final results and to confirm the concentration of the bacteria.

The pipes from Suen's office are also thought to connect, at a distance, with the offices of the Development Bureau, Home Affairs Bureau and Labour and Welfare Bureau in the west wing.

Microbiology professor Ho Pak-leung, of the University of Hong Kong, told Cable TV that the bacteria are usually found in older water supply systems

'The new government headquarters should theoretically be more modern than the older ones. It's disappointing that such bacteria are found only several months after moving in. Usually they are found in older buildings where pipes are dated and whose maintenance and designs aren't done properly,' he said.

'Now that the bacteria are found, the water supply system must at least be cleaned, and the design of the water supply system must be examined,' he said.

Meanwhile, the centre advised all departments in the complex to install water filters in pantries and provide alcohol dispensers on all floors, a spokesman for the Administration Wing said yesterday.

Water Supplies Department staff will investigate and see if there are problems with the building's water supply system. More water samples were taken from the office building to conduct further tests yesterday. Samples were also taken from Suen's home, but were clear of the bacteria.

A Department of Health spokesperson confirmed that samples were taken from Suen's office on December 22, the day after he was diagnosed with legionnaires' disease.

He was admitted to Queen Mary Hospital on December 18 initially with pneumonia. According to Tsang, Suen's condition was stable.

But it was up to Suen and his doctor as to when he could leave and whether he would be able to undertake demanding tasks in future.

In July, managers on the Tamar project revealed construction was behind schedule, threatening to delay the government's relocation.

The complicated design of the complex - which will house more than 3,000 civil servants when operating at full capacity - meant it took longer to build than anticipated.

Health check

Disease acquired its name after an outbreak of pneumonia among people attending a convention of the American Legion at a Philadelphia hotel in July 1976

The bacteria is called legionella pneumophila

Symptoms can include fever, chills, coughing, headaches and muscle aches

The bacteria grows in warm conditions such as water tanks, cooling towers, central air conditioning systems, whirlpools and spas, water fountains and breathing apparatus

High-risk groups include the elderly, diabetics, smokers, people who drink alcohol or have weakened immune systems

Fatality rate is between 10 and 15 per cent