An American passenger plane has been quarantined at a California airport after four people on board reported symptoms similar to a deadly pneumonia that has spread across the globe, airline officials said.
In Hong Kong more than 200 cases were reported in one building
The news comes as an expert warned that the disease - which is thought to have originated in the Far East - could be more contagious than previously thought.
It also claimed two more lives in Canada on Tuesday, bringing the number of deaths worldwide to 64, while more than 1,800 people have been infected.
American Airlines Flight 128 from Tokyo is being held on the tarmac at San Jose International Airport after two passengers and two crew members complained of feeling unwell, airport officials said.
The plane was stopped shortly before it reached the gate and ambulances lined up near the gate as passengers and crew remained on board.
A spokeswoman for the local health department said those who reported feeling unwell would be taken for a chest X-ray and would have their travel history checked.
Others on the plane will be given medical advice and allowed to depart but must immediately contact a doctor if they develop any symptoms.
"This thing seems to spread a little easier than first anticipated, so we want to take every precaution," Joy Alexiou said.
Meanwhile other parts of the world are struggling to contain the deadly pneumonia virus, known as Severe Acute Respiratory Syndrome (Sars).
The World Health Organisation said on Tuesday that outbreaks have effectively been contained in Vietnam, Singapore and Canada.
However in Canada two more people died from Sars, health officials said on Tuesday, raising the death toll in the country from the disease to six.
But Hong Kong, which has been hit hard, has now established quarantine camps in an effort to try to contain the spread of the disease.
And at Singapore airport, nurses have been monitoring passengers for signs of the illness. Seven were sent to hospital because they showed symptoms of the pneumonia.
Initially it was thought that the illness could only be spread by close contact.
But Dr Hitoshi Oshitani, a World Health Organisation (WHO) expert, told the BBC that this was not necessarily the case.
He said: "In most cases infection occurs by close person-to-person contact, but there are several cases now that we cannot explain by this model of transmission."
More cases of Sars have been reported, with Hong Kong health chiefs announcing 75 new cases on Tuesday - making a total there of 685 cases and 16 deaths.
More than 200 cases have been reported among residents in an apartment block in urban Kowloon.
Health chiefs initially placed the remaining residents of the Amoy Gardens complex in quarantine to try to block further spread of the disease.
But on Tuesday when it became clear this strategy was not working, they began to move residents out to disease quarantine centres set up in holiday camps.
Other developments on Tuesday included:
The first suspected case reported in Australia, a British tourist who has recovered and returned home.
The first three suspected cases reported in Indonesia.
A hospital in Ipoh, Malaysia said it had quarantined several patients suspected of being infected for several days.
Three new cases reported in Singapore, where nurses screening arriving air passengers found seven sick enough to send to hospital.
China 806 cases (34 deaths)
Hong Kong 685 (16)
Singapore 92 (4)
Vietnam 58 (4)
Canada 129 (6)
Sars is thought to have originated in southern China, but has spread to many other countries, including Vietnam, Taiwan, France and Germany.
French authorities are the latest to advise against travel to Hong Kong or mainland China.
Last week, the US, Canada, the Republic of Ireland and Australia also issued advice to cancel or "re-consider" trips to the affected regions.
China Airlines, Thai Airways, Cathay Pacific and Dragonair have cancelled or reduced flights.