LILLE, France (REUTERS) - Three people who came into contact with France's only confirmed case of coronavirus have tested negative for the Sars-like disease, with results pending on two others, Health Minister Marisol Touraine said on Saturday.

Lab results were expected later in the day on a friend or family member of the infected man, who remains in serious condition, and another patient who shared his hospital room, the minister and doctors told reporters in Lille, northern France.

A doctor, a nurse and a third health professional who had come into contact with the 65-year-old confirmed to have coronavirus are in the clear.

Health experts are concerned about clusters of new possible cases of coronavirus, or nCoV, which started in the Gulf and spread to France, Britain and Germany. But there is so far no evidence of sustained human-to-human transmission.

The French-confirmed case, hospitalised in Lille, was diagnosed after returning from the United Arab Emirates.

The friend or family member treated as a possible coronavirus case has been isolated at home pending results, officials said. The young man's condition is "not worrying", according to Lille hospital doctor Benoit Guery.

The World Health Organisation (WHO) has raised the number of cases confirmed worldwide to 33 after Saudi Arabia said that two people who were admitted to hospital there in April had been determined by laboratory analysis to be infected.