Fears that animals carrying Sars-like viruses could trigger another outbreak have been heightened by a testing programme.
Scientists from hospitals in Hong Kong visited a market in Guangdong province in China - thought to be the source of an illness which killed hundreds.
In several animals, reports the journal Science, they found viruses similar to those which caused Sars.
Some healthy people were also carrying these viruses, they found.
The research, reported in the journal Science, focused on a live animal market in Shenzhen, and sampled seven wild, and one domestic species.
The animals tested included civet cats, raccoon dogs, a ferret and a badger.
Scientists have been looking for a "reservoir" of the coronavirus which is believed to have "jumped" from animals to humans to cause the first Sars infections.
This spread rapidly around south east Asia, causing more thousands of cases of a severe pneumonia illness.
Dozens of deaths were also caused by Sars in the Canadian city of Toronto.
While a massive response by public health experts managed to halt the spread of the virus, there is growing conviction that Sars has not been eradicated.
Many expect there will be another outbreak of a Sars-like illness, perhaps starting later this year - and probably starting again in southern China, where conditions are most likely to allow similar viruses to jump from animals into humans.
The World Health Organisation has introduced a new method of looking out for suspicious cases in southern China.
The Hong Kong team managed find coronavir viruses in the two palm civets, one raccoon dog and one ferret badger.
They also found people who worked at the market carrying coronaviruses - without any sign of illness.
The civet coronaviruses were genetically "sequenced" to see if their coronavirus was similar to the one which caused Sars.
While there were plenty of similarities, there were clear differences, and the experts are still unsure exactly how viruses such as these - which may be common in wildlife in the area - managed to cross the species barrier and become dangerous viruses for humans.
The researchers said that the markets, with large numbers of humans working in proximity to wild animals, were a venue for viruses to "amplify and transmit to new hosts".
They wrote: "Because of the culinary practices of southern China, these market animals may be intermediate hosts that increase the opportunity for transmission of infection to humans.
"Further extensive surveillance on animals will help to better understand the animal reservoir in nature and the inter-species transmission events that led to the origin of the Sars outbreak."
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