Experts from the ministry of science and technology and the ministry of health are fanning out across the nation, Beijing News reported.

The move follows the closure of China's top laboratory on the SARS epidemic due to the widespread belief that the latest outbreak of the respiratory disease started at the Beijing-based Institute of Virology.

The World Health Organisation is also sending a team to China to investigate how the infection happened and to check whether internationally accepted bio-safety guidelines were compromised.

Chinese authorities say a researcher at the institute contracted SARS and infected a nurse who took care of her at a Beijing hospital. The respiratory ward at the hospital has also been closed.

The researcher's mother has since died, while the nurse's relatives and contacts have also gone down with symptoms of the disease.

So far there are six suspected and two confirmed cases, while 337 people have been isolated in Beijing and 133 in Anhui province.

The confirmed patients, surnamed Li and Song, are said to be in a stable condition and their body temperatures are normal, state media reported.

No new cases were reported Monday.

While the threat is not yet considered serious to public health, there are fears the disease may have spread widely through the rail network, the World Health Organisation (WHO) said.

The WHO is concerned that the outbreak could turn into an epidemic because the medical researcher had taken long train journeys after contracting the disease.

"Because of the long train journey it is not so easy to trace all of the possible contacts," WHO Western Pacific regional director Shigeru Omi told a news conference in Manila.

"From our experience with SARS last year we know hospitals have a tendency to amplify the infection."

But he said: "We do not see this yet as a serious public health threat."

Last year SARS killed nearly 800 people and infected more than 8,000 worldwide, with China being the worst hit country, and there are concerns that the Labour Day holiday next week could exacerbate a spread of the latest outbreak.

During the holiday, millions of Chinese will be on the move by train, bus and plane.

Vice Minister of Health Zhu Qinsheng said anti-SARS measures had been stepped up ahead of the week-long break.

"Our airports and ports are taking measures to ensure things will go smoothly," Zhu said in Malaysia.

"We have resumed temperature screening in airports and railway stations. Passengers are also required to fill in health declaration forms."

Meanwhile, all hospital across the country at county level and above have been ordered to conduct urgent checks on deaths related to pneumonia dating back to March 2.

No suspicious cases had been found so far, the health ministry said.

TERRA.WIRE