The World Health Organization (search) on Friday downgraded its assessment of SARS (search)-prevention efforts in Canada after a U.S. visitor to Toronto returned home with the virus. But the U.N. agency said it had no plans to issue another travel advisory for the city.

WHO officials also dropped some parts of China from its list of places under the SARS travel warning but retained its advice that people avoid nonessential travel to Beijing and Taiwan.

On Saturday, Taiwan reported two SARS deaths, breaking a period of 16 successive days without new fatalities. Taiwan also announced one more person had become infected.

Taiwan has the world's third-highest number of SARS cases and fatalities, behind mainland China and Hong Kong.

Taiwan on Friday began investigating whether the island underreported SARS deaths. Authorities have begun examining a large discrepancy between SARS numbers compiled by the Health Department and local governments.

The Health Department (search) says SARS has killed 83 people on the island, local governments have reported cremating 363 bodies, including suspected and confirmed SARS cases, said Chao Chang-ping, a member of the government's official watchdog body, the Control Yuan.

In Geneva, the WHO placed Toronto in a more severe category of SARS transmission because of the case involving a North Carolina man who visited a geriatric care facility that had not previously been known to have any SARS cases.

Toronto appeared to have brought the outbreak under control until May 22, when a second cluster of cases was reported.

"Toronto let down its guard in mid- to late-May," said WHO spokesman Iain Simpson said. "Somewhere along the line, the surveillance system wasn't effective enough or someone wasn't vigilant enough and cases got through the net."

The U.N. health agency shifted Toronto from Pattern B to Pattern C, its most severe category.

The Pattern B category means that the disease is spread among people who have had known contact with probable SARS cases. Pattern C means that there are cases among people who were not previously identified as known contacts of SARS cases and who therefore raise new questions about whether the disease has been contained.

The classification is a technical device to help epidemiologists keep track of the virus.

Health officials in Toronto said Friday they may have found the link between the city's first and second SARS outbreaks. They say a nurse contracted the illness from her heart-patient mother at one hospital and passed it on to a man at another hospital where she worked.

The nurse's illness links Scarborough Grace Hospital where the Toronto outbreak began in early March and North York General Hospital where the second outbreak in May had been traced to a 96-year-old man.

The U.S. Centers for Disease Control diagnosed the American with SARS on Monday and placed him under quarantine with his family near Raleigh, N.C. Simpson said the U.N. health agency was concerned because nobody had previously been aware that the geriatric facility in question was linked to the SARS outbreak.

In North Carolina, state officials Friday said two men who worked in the same building as the SARS patient came down with pneumonia, and one of them died Friday of heart failure and pneumonia. Both men tested negative for SARS and follow-up testing is being done, said state health director Leah Devlin.

The three men, who have not been identified, worked in the same building at the University of North Carolina at Chapel Hill.

With 33 deaths and 238 cases, Canada is the hardest-hit country outside of Asia. Its economy was hit hard by a WHO travel advisory in April.

Dr. Paul Gully, a Canadian federal health official, said the WHO action amounts to a criticism of the country's efforts to track the spread of the virus.

"It is an interpretation of the adequacy of contact-tracing in Canada," he said.

Gully said the nation was adopting a tougher quarantine law that give health officials more authority over airlines.

Under the regulations, airlines would be required to distribute SARS information cards and questionnaires on incoming flights, a practice that is now voluntary, he said.

So far, SARS has killed nearly 800 people worldwide and has infected more than 8,400.