The sisters, aged 3 and 5, were found unconscious by family members. They were rushed to a hospital in Red Deer in critical condition before being transported by helicopter to Edmonton.
Officials say they don't know how long the sisters were submerged in the icy water for before they were found. Several media reports Saturday have indicated that the younger of the two girls had died, and that the older one remains in critical condition. RCMP has stated that they would no longer comment on the condition of the children, out of respect for the family.
Police say ice conditions in Alberta are poor because of recent warm weather -- Alberta has seen record-breaking warm temperatures over the past month.
Even though the weather is warming up, water below unstable ice is still frigid -- and officials say hypothermia can set in very quickly.
With files from The Canadian Press