Martha Villanueva, 53, and Ernesteen Villanueva were identified by the medical examiner Saturday, however, their exact cause of death has not yet been determined.
Four others, including three children, were also hospitalized with apparent carbon monoxide poisoning, according to officials.
A neighbor called 911 when they smelled gas coming from a home in the 2800 block of West 22nd Place, according to Chicago Fire Department spokesman Larry Merritt.
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Firefighters forced their way into the home at 1:40 p.m. and found the two woman, in their 50s and 70s, dead in the basement of the home.
Ernesteen and Martha were mother and daughter, according to neighbors.
Officials said four others on the floor above, an adult and three children, were taken to a hospital. Neighbors said they appeared to be conscious and talking.
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The source of the carbon monoxide is still being investigated, but fire officials say the levels detected in the home were about 20 times higher than what's considered safe.
Fire officials said it does not appear there were working CO detectors on every floor of the house.
"We gotta make sure that carbon monoxide detectors are on all levels in here, and they are our first line of defense to protect us from any type of events such as this," said Acting Dep. District Chief Barry Garr, Chicago Fire Dept.
Neighbors said the victims are from two separate families, and they say two of the kids who are hospitalized are teenagers. That third child is about five years old.
The Sun-Times Media Wire contributed to this report.
The video featured is from a previous report.