Friday's party was the third time the Mont Cascades resort in Cantley, Que., north of the Ottawa-Gatineau area rented out space for the annual Spookland party.
MRC des Collines police say they are now investigating at least three allegations of sexual assault, and they expect a fourth person they have spoken with will file a report.
Police spokesman Martin Fournel says one 16-year-old girl "was found on-site, half-dressed, and under the influence of GHB” — also known as the date-rape drug.
Two other girls have alleged they were fondled while waiting in line to get in to the event.
Chartered busloads of teenaged partiers were bused from the Ottawa area to the Spookland bash.
Police have said many of those on the bus were drinking on their way to the event and were not properly screened before being let in.
A total of nine people were taken to hospital with drug and alcohol-related ailments and one teen spent the weekend in the intensive care unit with a blood-alcohol level six times the legal limit.
The party was organized by an Ottawa-based company.
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