Police say Guadalupe Ramirez, who lived in the same apartment as the boy, died at the hospital Sunday.
Investigators say snow drifts happening at the time of the fire helped them extinguish the flames.
The fire spread to several buildings and forced 250 people from their homes. Eleven people were sent to hospitals..
Detectives are trying to determine what caused the fire. They don't believe it was set deliberately. It started in a third-floor apartment on Paul Road North around 6:20 a.m.
Some 300 firefighters were called in from 13 departments. It took several hours to extinguish the fire.
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