Huron County OPP were called to an area on an OFSC (Ontario Federation of Snowmobile Clubs) trail at C Line Road near Wroxeter around 12:30 early Saturday morning.
They along with Huron County paramedics and North Huron Fire Department found two people, a 25-year-old from Morris-Turnberry and a 25-year-old from Teeswater, with serious injuries.
The West Region Traffic Incident Management and Enforcement Team were brought in to assist in the investigation.
OPP say alcohol and speed may have been a factor in the crash.
They are reminding snowmobilers that trails remain closed at this time and anyone caught on a closed trail may be charged with trespassing.