Officials said that a train was quarantined in Canada on Friday after one of the passenger's died from a mystery illness.
But the emergency was soon deflated after laboratory tests found no evidence of infectious disease.
Police and ambulances rushed to the scene in the early morning in the hamlet of Foleyet, a tiny community of less than 300 in northern Ontario, some 800 kilometers (500 miles) north of Toronto, to tend to those with flu-like symptoms and find out what was causing a "mystery" illness.
"At nine o'clock this morning, we were notified of an ongoing emergency health situation that was occurring on a Via passenger train which ... was heading to the Toronto area," said Ontario Provincial Police Constable Marc Depatie.
The Via Rail train traveling from Vancouver to Toronto was immediately quarantined, he said.
A woman in her 60s was found dead and six people were ill with flu-like symptoms when the trans-Canada train with 260 passengers and 30 crew made its regular morning stop in Foleyet.
One person was taken by helicopter to an area hospital and was in "stable condition," said Emergency Medical Services regional director Steve Trinier.
Meanwhile, medical personnel tried to determine if there was an infection or communicable disease at play, or whether the sudden sickness was due to toxic environmental exposure, or even food poisoning, he said.
Health Minister Tony Clement also directed federal officials to liaise with provincial, regional and local authorities "both in Foleyet and at all points along the route the train traveled," he said in a statement.
By mid-afternoon, however, officials began to downplay the emergency after tests indicated no presence of an infectious disease and said the train would likely get underway later in the day.
"It has been determined that the deceased did most likely not have an infectious disease," Ontario medical officer David Williams told a press conference.
A passenger who was airlifted to hospital also "does not have an infectious disease," he said.
And five passengers who were isolated on the train were found to have had only "minor" symptoms.
What caused the one passenger's death "is unknown at this time," Williams added. But "it has been determined that the evacuation of surrounding communities is not necessary."
One passenger who sat in the same coach as the deceased woman reported shortness of breath, but doctors determined that it was likely "an exacerbation of an underlying medical condition," Williams said.
Of the five who "felt unwell before they got on the train," one of them had seen a doctor in western Canada before the trip and was diagnosed with a viral or sinus infection that was treated with antibiotics, he said.
Earlier, Michael Gardam, director of the University Health Network's infection prevention and control, had predicted the quarantine was just a "precautionary measure."
He pointed out that panic and fear in 2003 overwhelmed Ontario's capital Toronto, also the nation's largest city and economic hub, after some 400 cases of the often deadly Severe Acute Respiratory Syndrome (SARS) were reported.
Related emergency healthcare costs, lost tourism revenues and other economic fallout in Toronto topped one billion dollars.
"The reality is you have to take these things seriously, even though usually they turn out to not be anything particularly serious," Gardam said.
Police said the dead woman had boarded the train in Jasper, Alberta. They are now investigating possible foul play, Constable Depatie told AFP.