The World Health Organization says a top Beijing laboratory is to blame for the newest SARS cases in China.
The WHO regional director in Manila (Shigeru Omi) says safety guidelines were not followed and some sort of "mistake" happened at the research institute.
The organization says it is sending a team to China to investigate how a medical student was apparently exposed to the virus at the facility and became ill.
The research lab has been closed, and authorities have published details of the original patient's recent travel, so people can determine whether they might have been exposed to the disease.
There have been two confirmed Severe Acute Respiratory Syndrome cases in the country since Friday. Health officials say they have isolated another six suspected cases.
China says it is sending emergency inspection teams to check security at other laboratories around the country.
The WHO says the new SARS outbreak is not yet a serious threat to public health, but does require heightened vigilance.
The U.N. health agency says it is particularly worried because of the approaching May Day holiday (beginning on Saturday) -a week-long period when millions of Chinese travel around the country by plane, car and bus.
Malaysia is the latest country to announce it is reactivating screening procedures and other precautions against the spread of the disease.
Severe Acute Respiratory Syndrome is believed to have originated in China. The pneumonia-like disease killed more than 800 people last year, most of them in Asia, and infected thousands of people in at least 30 countries.
Information for this report is provided by AP, AFP and Reuters.