BEIJING - One of two confirmed SARS patients in China was recovering and "in a fine mood" Tuesday as the government stepped up scrutiny of pneumonia cases and awaited a team of international health experts who will investigate how the disease flared up again.

The country has announced six new suspected cases in recent days, all linked to a Beijing research lab where investigators suspect that workers caught and spread severe acute respiratory syndrome.

The World Health Organization said it would dispatch a team in the coming days to find out how two lab workers at China's Centers for Disease Control could have become infected and why their ailments weren't monitored. It was unclear when the team would arrive.

Authorities say a lab worker named Song in Beijing passed SARS to a nurse named Li, and the nurse's father, mother, aunt and roommate have fallen ill as well. Song returned to the southeastern province of Anhui and her mother died shortly thereafter. Experts suspect SARS was the cause.

The official Xinhua News Agency said Tuesday that Song, 26, was in stable condition. It quoted Zhu Qixing, head of the No. 1 Hospital at Anhui University of Medical Sciences, as saying Song had a normal temperature and was "no longer infectious."

"She is in a fine mood and can do some exercises out of bed," Zhu was quoted as saying.

China, meanwhile, is pushing to contain the apparent outbreak ahead of a national holiday when millions of travelers - and potential disease vectors - start traveling around the country.

Pneumonia cases at hospitals above the county level in China are all being examined to determine if there are any SARS links, the state-controlled newspaper Capital Times reported Tuesday. The symptoms of pneumonia and SARS are very similar, and SARS was originally classified as "atypical pneumonia."

Hundreds of people Beijing and Anhui remained under quarantine Tuesday after possibly coming into contact with cases or suspected cases. The already daunting task was made especially urgent by the week-long May Day vacation, which begins Saturday.

Some 337 people have been quarantined in Beijing and 133 in Anhui, the official China Daily said Monday. On Tuesday, other state-controlled media said the number was about 600, though it was unclear if the amount of isolated people had actually increased or if that was simply a reporting discrepancy.

WHO, citing the Chinese government said "close to 1,000 contacts of these cases are under medical observation" but didn't say if they were actually quarantined.

SARS triggered a global health crisis last year, killing 774 people around the world and infecting more than 8,000 before subsiding in July.