More SARS deaths were being reported Thursday in various countries after a suburban Toronto parochial high school was closed, and 1,700 pupils and staff told to stay home for 10 days, after a student showed symptoms of the deadly disease, health officials said.

Father Michael McGivney Catholic Academy (search) in Markham, Ontario, will not hold classes until June 3.  Local officials expected the number of suspected cases to rise.

The moves raise to more than 5,000 the number of people in the Toronto area under quarantine as authorities seek to control the spread of a new cluster of SARS cases known to have infected 11 people and to be suspected in 23 others.

Two more elderly patients died, raising the overall SARS toll to 29 deaths in the Toronto area in the biggest outbreak of severe acute respiratory syndrome outside of Asia.

Dr. Colin D'Cunha (search), the Ontario commissioner of public health, who announced the deaths and latest figures, said 50 more cases were under investigation and the number of probable or suspected cases will rise.

"Absolutely there will be more in the next few days," said Dr. James Young (search), the province's commissioner of public safety.

"This is a problem that is serious, but it is not dangerous at all to travel to Toronto," added Canadian Prime Minister Jean Chretien during a visit to Athens, Greece.

Meanwhile, Russia reported its first case of SARS — a man living in Blagoveshchensk (search), in southern Siberia along the Amur river, which forms the frontier with hard-hit China, Reuters reported.

Taiwan reported 50 new cases Thursday, although health officials said many of those cases had been suspected for a while.

The Hong Kong government said on Thursday that the virus had killed three more people and infected two others in that territory, Reuters reported. Thursday was the 15th straight day the number of new infections had been five or less. Hong Kong's SARS death toll is now 273 and the number of cases has reached 1,732.

China also reported two more people had died from SARS and another three were infected on Thursday. One of the deaths, and all three new cases, were in hard-hit Beijing. China has now had 327 deaths and 5,325 cases, and has threatened fines for people who break health rules.

The first SARS outbreak in Toronto began when a woman returned from a February trip to Hong Kong bearing the disease.

The 78-year-old woman died on March 5 and her son a week later, but not before the disease had spread to several other people, including patients and health-care workers at the Toronto hospital where they had been treated.

Thousands of people were later quarantined as health officials raced to contain the outbreak. Toronto was removed from the World Health Organization (search) list of SARS-affected areas on May 14 after more than 20 days passed without a new case being reported.

But the WHO put Toronto back on the list after the latest cases were made public last week. The current outbreak may have originated with an elderly patient whose case dates from April 19.

On Wednesday, the WHO advised Canada to broaden its definition of SARS cases after a health official voiced concern that the current one wasn't accurate.

Dr. Donald Low, a microbiologist and key figure of the anti-SARS team dealing with the Toronto-area outbreak, said the number of new probable cases would be well over 20 if officials used the same definition applied during the initial outbreak in March and April.

On the Health Canada Web site Wednesday, a probable case was defined as someone showing a severe progressive respiratory ailment — a more serious condition than the WHO definition, a respiratory ailment visible on a chest X-ray.

Dr. Paul Gully, a federal health official, said revising the definition was being considered and said that such a change would cause some suspected SARS patients to be classified as probable.

Officials worry the WHO could issue another warning against travel to the city, like one on April 23 that was lifted a week later. A travel advisory is tougher than Toronto's current listing as a SARS-affected area.

D'Cunha, the Ontario provincial health commissioner, said the criteria for such an advisory were 60 or more probable cases, five new probable cases a day and proof the illness was being exported to other countries.

The possible exposure at Father Michael McGivney Catholic Academy involved a student who attended school last week while feeling ill, officials said. The student is the son of a health care worker linked to a Toronto-area hospital with known SARS cases and also displaying SARS-like symptoms.

On Wednesday, the student was listed as a suspected case of SARS, but Dr. Murray McQuigge, a York Region Public Health official, said there was no doubt.

"We're saying this person does have SARS. This is deadly serious business," McQuigge told a news conference.

WHO spokesman Dr. David Heymann (search) said Wednesday the U.N. agency always knew Toronto could face a renewed outbreak, and there were no plans to re-impose a warning against travel to the city.

Health authorities re-imposed strict controls on Toronto-area hospitals — closing those where the new cases were found to new patients and limiting access to emergency rooms in all others.

The Associated Press contributed to this report.