Ontario public health officials expressed concern today they could lose the battle to contain the spread of SARS, because some people with symptoms are breaking quarantine to wander about in public.

Authorities today discussed forcibly confining a man they said was becoming belligerent and uncooperative with public health authorities. The unidentified man, a health care worker, attended funeral services while he was showing symptoms of the sometimes fatal respiratory ailment. Officials were seeking hundreds of people who may have been exposed.

"It is a result of one person's lack of responsibility that, unfortunately, other people have been put at risk," said Hanif Kassam, acting medical officer of health for York, a suburb of Toronto. Kassam said the man attended a wake at Ward Damiani Funeral Home in Woodbridge, a suburb of Toronto, Friday and Saturday. He also attended a funeral Mass at St. David Catholic Church in Maple, another suburb, on Saturday.

"Placing everyone attending this event in quarantine is an aggressive, yet effective, method to prevent the further spread of SARS," Kassam said. "It will only work, however, if individuals come forward and agree to follow quarantine directives."

Officials also sought people who rode a commuter train with a nurse who was suffering from SARS symptoms. The nurse took the train from Burlington, a suburb of Toronto, to downtown Toronto during morning and evening rush hours last week, officials said. They said six people seated close to her were of particular concern.

"If we knew who those six were, we would have just identified them and dealt with them," said Bob Nosal, a regional medical officer. "The reality is we don't know."

Canada has the highest number of SARS cases outside Asia. Authorities have reported 14 deaths from the illness since March 5, when a woman who had contracted SARS returned to the country from a trip to Hong Kong. Officials said they were investigating one other death. Health officials reported at least 316 probable and suspected SARS cases in Canada, including 135 probable and 124 suspected cases in Ontario. The World Health Organization reported 132 probable cases in Canada.

There were also reports that some health care workers, vulnerable because of frequent contact with SARS patients, appeared to become infected despite wearing protective gloves, goggles and masks. This weekend, officials closed a critical care unit at Sunnybrook hospital in Toronto after four health care workers showed apparent symptoms of SARS. Today, officials said they believed the workers had become ill because of breakdowns in isolation techniques. "Not through anything they were knowingly doing, but in fact from fatigue and inadvertent breakdowns," said James Young, Ontario's public safety commissioner.

Officials instituted new measures in SARS units at hospitals, including requiring nurses and doctors to wear full face masks and double gloves. Ontario officials asked Canadian federal officials and scientists from the U.S. Centers for Disease Control and Prevention to come to Ontario, audit measures taken here and give advice to make hospitals safer.

For weeks, officials have cautioned the public not to panic, saying all cases could be tracked to two clusters: people who have traveled to Asia or their relatives and health care workers who treated them. Last week, officials begin investigating a third cluster: 29 people who belong to a Roman Catholic sect called the BLD Covenant Community who attended a prayer group on March 28 and March 29. Two doctors who treated them were also infected. Officials asked 450 members of the group to go into quarantine.

In the United States, a Pennsylvania man, who apparently become infected with SARS when he attended a religious meeting with the group, improved enough to be released from the hospital, officials said . The man was instructed to stay home for at least another week to prevent him from infecting anyone else. State and federal health officials are monitoring everyone he had contact with for symptoms of SARS. U.S. health officials are investigating 228 suspected SARS cases in 35 states, including six in Virginia.

World Health Organization officials reported they were concerned about cases among the close-knit religious group. "The outbreak," the WHO reported, "is particularly disturbing because of its potential to move into the wider community." WHO officials said the outbreak would be considered a "test case" of whether tracking down cases and stringent quarantines could stop the further spread of the disease even when a crowd of people has been exposed.

Officials in Toronto, meanwhile, reiterated quarantine warnings. "I would like to again remind everybody, including health care workers, who are experiencing SARS symptoms to go into isolation," said Colin D'Cunha, Ontario's public health commissioner. "Please don't leave isolation. Doing so could imperil your own personal health, the health of your family and close personal contacts."

Young said Ontario may be dealing with SARS for the long term. "The cases where we are seeing the spread, people are sick and in some cases may or may not realize how sick they are but they are out in the community for several days before they seek medical attention or before medical personnel recognize it," Young said. "During that period of time they are clearly very infectious. It appears from what we are seeing: the sicker people are the more they are capable of spreading this disease."

Staff Writer Rob Stein contributed to this report from Washington.

Bob Nosal, an Ontario health officer, is among those looking for people who rode a commuter train with a nurse with SARS symptoms.A volunteer disinfects pews at St. David Catholic Church in suburban Toronto. A health care worker showing symptoms of SARS attended funeral services at the church last week, potentially exposing hundreds to the illness.