Firefighters found the bodies of 2-year-old Javaris Meakens and his sister 3-year-old Jariyah Meakens when they responded to the fire on the 6400-block of South Paulina at about 3:30 a.m.
The Chicago Fire Department has turned the case over to police and criminal charges could be filed against the mother for leaving children home alone. Police said no charges have been filed yet in connection with the fire
The victims' mother and aunt were questioned by police Saturday afternoon, according to police.
The preliminiary investigation indicated that the fire was accidential, according to fire officials.
The childrens' two male cousins, 7-years-old and 4-years-old, were also in the home. The two boys made it out with the help of their mother and were in the custody of DCFS later Saturday.
The older boy told neighbors that all four children were left alone in the house.
"They were just standing there shivering. No coat, no shoes," neighbor Michelle Washington said. "When we brought them in, they told us their aunt and their mom left them in the house alone. Told them to go to sleep."
"They heard the little baby crying, beating on the door," neighbor Tiffany Williams said. "But they couldn't go back and get her because they were choking on the smoke."
Rescuers arrived to find flames shooting from the first floor bedroom window of the home.
Firefighters tried to cut bars on the windows to get inside and help the victims, but the flames were already too powerful.
The children were found dead in their bed inside a back bedroom of the basement.
The fire started in the basement, authorities said, and spread to the first floor of the brick home.
A hot plate could have sparked the fire, according to officials.
ABC7 has confirmed there were no adults at home with the children at the time of the fire.
"I've lived in this community for 41 years, and I'm like, 'Do I know these children?' and walking down the block, I literally broke down," Ald. Toni Foulkes said.
There was a solemn remembrance at the scene of the deadly fire Saturday night.
Neighbors released balloons into the air in honor of the two children.
"Everybody's like grieving right now. Everybody's hurt, sad. Trying to get peace," family friend Naisha Williams said.
"They meant a lot to everyone that's here. That's why we're all here," family friend Lawana Coleman said. "We're sticking together because if it wasn't one of their kids, it could've been one of our kids."
Neighborhood residents Armani Martin and her sister expressed their grief by leaving two stuffed animals.
"We just thought it was sad because they died," Martin said.
"You don't want to hear anything like that this close to the holidays, and by being children, you know you don't want to hear that," said neighbor Lorraine Jackson, who ran over to help.
Fire officials said there were no working smoke detectors in the home. Firefighters were expected to canvas the neighborhood Saturday to pass out free smoke alarms.