The Mundelein Fire Department responded to a report of a fire in the 1200-block of Huntington Drive around 5:30 p.m.
Officials originally said the elderly woman was suspected missing.
On Monday, the fire department confirmed the woman's body was found in a second-floor bedroom.
Foul play is not suspected. Her identity has not been released.
Officials added that getting into the house was difficult due to the hoarding conditions.
There were mounds up to 5-feet high throughout the house, including the stairs, officials said.
"Upon arrival, the front door could only be opened 5 to 6 inches, and had to be removed off its hinges," officials said.
The house had no central heating. Officials added that they found space heaters and propane-powered camping-type heaters.
Further information was not immediately available.