The Ontario Provincial Police say crews are searching for a 22-year-old woman from Scarborough who went missing in the Papineau Lake waters in Hastings Highlands on Saturday evening.
Officers from the Bancroft detachment responded to the incident just before 8 p.m.
Police said a woman had fallen off a floating device while she was in the water, and did not make it back to shore.
An area search commenced with the assistance of the OPP Emergency Response Team.
The searched resumed Sunday with the help of the Underwater Search and Recovery Unit.
The news comes as OPP continues to search for an 8-year-old boy who went missing in Lake Erie from Turkey Point on Saturday afternoon.