OTTAWA, Oct. 1 (Xinhuanet) -- Four people were dead and dozens of residents of Canada's biggest city of Toronto have been taken to hospital after an outbreak of a mystery respiratory illness, officials said on Saturday.

    Toronto Public Health experts told reporters 68 residents and five employees at Seven Oaks home for the aged in the city's east end have come down with the illnesses, according to local reports.

    Among them 15 were admitted to hospital -- four died on Friday, said Dr. Barbara Yaffe, adding that three of the victims died at the home, with the fourth dying in hospital.

    All of the patients had pre-existing medical conditions and two were in their mid-90s. The other two victims were in their late 70s and 50s.

    So far the source of the "typical respiratory illness" has not been found.

    "We know from testing that it's not influenza, not SARS, not avian influenza," said infectious disease specialist Dr. Alison McGeer.

    Officials at Rouge Valley Centenary Hospital, where many of the illed were taken, said they're monitoring the patients' conditions and that there is no quarantine or closure in effect.

    Some emergency rooms are taking extra safety precautions to protect patients and staff. Enditem