Thousands of civets are being killed in southern China after genetic tests link a case of Severe Acute Respiratory Syndrome to virus samples taken from some of the animals.

Chinese television reports showed health workers in protective suits removing civets from food markets as a cautionary measure against another SARS outbreak.

Across Guangdong province, where civets are sold as a delicacy, authorities were drowning the small nocturnal mammals in vats of disinfectant or electrocuting them before cremating them. Health authorities estimate 10,000 civets will be culled by the Saturday deadline to eradicate them from menus in southern China. The cull was ordered after virus samples from a Guangdong man with Severe Acute Respiratory Syndrome matched a strain apparently common in civets.

Peter Cordingly, the regional spokesman for the World Health Organization, says the agency is concerned that markets and restaurants where civets are sold will be driven underground.

That would make it difficult to study the possible link between SARS and animals and to track the source of outbreaks.

"We've long had our suspicions about the animal link to human cases of SARS, but we still think lots more research has to be done," he said. "We're also worried about this trade being driven underground... If this trade goes underground it will be more difficult to monitor."

SARS, which causes a serious pneumonia in most patients, spread to 8,000 people worldwide just months after emerging in southern China late 2002. At least seven hundred patients died before the outbreak faded in July last year.

Researchers in Hong Kong studied blood samples from animals sold in Chinese food markets, and think civets harbored a variation of the SARS virus that probably triggered the outbreak when it jumped to humans.

Some scientists, however, have questioned the findings. Wendy Fung, a researcher at Hong Kong bio-technology company DNA Chips, is one of them. "I question the authenticity of the testing they do because they didn't show a proper control that their method is not detecting other animal viruses," explained Ms. Fung.

The Guangdong man who was confirmed as having SARS on Monday has so far proved to be an isolated case, none of his close contacts have shown signs of the illness.

A state-owned Chinese newspaper reported he could have caught the illness from rats.