Officials have told people not to panic
China's health ministry has acknowledged a third suspected case of the deadly flu-like Sars virus in the southern province of Guangdong.
The 35-year-old man has been isolated in hospital for medical observation.
One of the suspected cases was confirmed earlier this month but the man has since recovered. The other, a waitress, is in a stable condition.
The initial case was China's first since the global outbreak last year that infected thousands and killed 800.
The latest suspect has not reportedly had any contact with civets or other wildlife which some Chinese officials have linked to the disease.
And so far, none of the 28 people with whom he has been in contact have developed any symptoms.
The BBC's Beijing correspondent, Louisa Lim, says reports of his case first emerged on Sunday in the Hong Kong media, and a spokesman for the World Health Organization (WHO) has expressed concern about how information on Sars cases is being released.
The spokesman told the BBC that the organisation was receiving confusing reports from various sources, including the media, rather than from official channels.
The WHO said the problem was compounded by differing views of what constituted a suspected case.
'Isolated cases'
The WHO describes the new suspected cases as isolated ones, rather than part of a cluster.
But our correspondent says there are still signs of growing unease, with local authorities urging people not to panic.
The authorities in Guangdong had ordered the culling of all animals that were suspected of carrying the Sars virus by 10 January.
Thousands of civet cats have been killed, mostly by drowning, electrocution and incineration, after researchers found links between the strain of the first Sars case and civets.
The cull was extended to badgers, raccoon dogs and other animals served as local delicacies.
The 20-year-old waitress in hospital worked in a restaurant serving wild animals.
The WHO delegation in Guangdong has promised to leave no stone unturned in its investigation.
It has warned there could be a number of suspected Sars cases in the coming months because of its resemblance to other winter illnesses.