"The number of people who have been isolated has risen to more than 600 because of the SARS epidemic," Wu Jiang, director of the infectious disease control department of Beijing Centre of Disease Control told the Beijing News.

The CDC confirmed the figure when contacted by AFP, adding that 24 of those under observation were staff from the national center of disease control.

At least 133 people are also in isolation in Anhui province, reports said.

"The people are either isolated in the same place or at home," said Wu, who expressed confidence that the Chinese capital would not be crippled by SARS as it was last year.

"At the moment the situation is under control. There is little possibility of the SARS epidemic affecting Beijing society," he said.

While the World Health Organisation has shown concern about bio-safety practices at the laboratory where the outbreak occurred, it backed Wu's assessment, saying the Chinese government appeared to be following all the right procedures.

"We still don't see this as a public health threat," WHO spokesman in Beijing Bob Dietz told AFP.

"We're pretty sure we've identified the source, the channels of transmission have been broken and we can trace it back to one source."

Meanwhile, two WHO experts arrived in Beijing Tuesday to investigate bio-safety standards at a top Chinese laboratory believed to be the source of the outbreak.

Chinese authorities last week said a researcher at the Beijing-based Institute of Virology contracted SARS and infected a nurse who took care of her at a Beijing hospital.

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 in Beijing and Anhui, although no new cases have been reported for two days.

In response to the scare, the Institute of Virology has been closed down and emergency inspection teams are being rushed around the country to check if health guidelines are being followed.

Dietz said four WHO teams were due to arrive in China over the next few days to look at bio-safety in laboratories, help in epidemiological investigations and to make sure hospitals have proper SARS precautions in place.

With the week-long Labour Day holiday starting Saturday, surveillance is being stepped up around the country to prevent SARS being spread by the millions of people taking train, bus and plane journeys.

Body temperature screening has resumed in airports and railway stations and passengers are required to fill in health declaration forms, the health ministry said.

Last year SARS killed nearly 800 people and infected more than 8,000 worldwide, with Beijing the worst-hit city in the world.

The Beijing Daily, citing Mayor Wang Qishan, said that a Beijing anti-SARS headquarters had been set up to deal with the crisis.

"The whole city should pay high importance to SARS and act immediately and decisively to sincerely implement important instructions by the central leaders ... to resolutely control the SARS epidemic," Wang said.

TERRA.WIRE