The Via Rail train quarantined by Canadian authorities after a passenger woman died and up to six others complained of flu-like symptoms arrived in Toronto on Saturday.

The train carrying 264 passengers and 30 crewmembers, sat for 10 hours in Foleyet, a small town in Ontario while health investigators tried to determine what killed the 60-year-old Australian woman, and why six other passengers became ill around her. Officials were keeping passengers from leaving the train, Steve Trinier, the director of ambulance services in the area, said, as quoted by CNN. He also added that the mysterious disease could be something as simple as food poisoning.

According to Dr. David Williams, Ontario’s chief medical officer, the woman who died on the train did not have an infectious disease and the illnesses were unrelated. “The origin of the illness that caused the passenger death is unknown at this time. Lab tests to date have eliminated a number of serious infectious illnesses,” he said.

However, Donald Low, a microbiologist at Toronto’s Mount Sinai Hospital said he suspected influenza. “This really points to something like influenza…Obviously this is a pretty acute event, a number of individuals sick with respiratory illness. We’re not talking SARS, we’re not talking avian influenza…We see this happen on cruise ships and other settings when you have people together in close confines,” he said.

The train arrived in Toronto on Saturday morning after resuming its journey late Friday afternoon. The investigation is ongoing.