Ottawa Public Health is investigating an outbreak of gastroenteritis after 60 of 125 teenagers attending a youth forum became ill.
Attendees of the Forum for Young Canadians were staying at the Capital Hill Hotel in Ottawa and ate most meals together at the hotel.
Ottawa Public Health said most of the teens became ill on Wednesday, but said a few cases may have happened as early as Sunday.
A few of the cases led to visits to local emergency rooms.
"In the first few days there were a couple of participants who weren't feeling well and it just went through the roof from there," said Cathleen Cogan Bird, the head of the Youth Forum.
"It's just very very unfortunate for these youth because they really look forward to coming and get a lot from their forum experience," she said.
Ottawa Public Health said they were not aware of any hotel staff or other guests reporting similar symptoms.
The youth forum attendees are teenagers between the ages of 16 and 19 and came to Ottawa from all ten Canadian provinces.