The authorities say there has been no known case of SARS infection from shipment of samples.

The source of the suspected SARS infection is therefore unclear at this stage.

Attempts were made to control further SARS infection through the use of quarantine.

Today's announcement came as the pace of new SARS infections in Asia continued to dwindle.

The two student cases bring to four the known SARS infections that have occurred in three laboratories since the disease was first detected last year.

But as SARS infections rose rapidly in Taiwan, China came under sharp pressure to allow the agency to play a direct role.

There was more good news this afternoon, when Hong Kong health officials announced that no new SARS infections had been detected in the preceding 24 hours.

Scientists have found evidence of SARS infection among animal handlers in the market.

Strict quarantine controls were in place because of fear of the SARS infection.

Researchers are currently trying to develop vaccines to prevent SARS infection.