The Chicago Bomb and Arson Unit is considering the investigation a criminal one. Police have been interviewing witnesses including the children's mother. No suspects have been named or charged in the case.
The fire started just before 11a.m. at a home at 8338 South Buffalo Avenue.
"My cousin didn't kill her kids. She did not kill her kids," said Ayesha Delaney, mother's cousin.
That was the sentiment on Wednesday night as relatives defend Danielle Cheatham.
On Wednesday evening, Cheatham's three children were being remembered with candlelight and stuffed animals placed in front of the family's home near 83rd and Buffalo Avenue.
Three-year-old Sharell Gates, her two-year-old brother Tyrell, and seven-month old brother Jimmy all died when a fire started about 10:40 a.m. on Wednesday.
Firefighters say Cheatham was in another part of the house when the fire started.
Police say they are questioning Cheatham, which is standard procedure.
"Somebody need to be there to hold her, to hug her," said Delaney.
Chicago's Bomb and Arson Unit is now investigating.
Fire officials say there was one smoke detector in the building, but it was not working.
Relatives say the natural gas had been cut off, but, somehow, it was rigged and turned back on. And there were also electrical problems. Relatives say everyone was aware of those, including the landlord.
"When I plug on my microwave, it gets pop and you can see the electricity bolts coming out of it when you plug it up," said Sharday Harper, victims' cousin.
On Wednesday night, relatives revealed details about a conflict inside the home between two men. Relatives say one tried to rob the other about a week ago.
"He said, 'they tried to rob me.' His neck was red, under here, his neck. He said, 'he tried to rob me,'" said Vaness Gordon, mother's cousin.
"I think everybody in the building needs to be investigated," said Delaney.
Since the alleged robbery, relatives say the male victim has not been back to the house.
On Wednesday night, the family's home was shuttered and crews were also boarding up the next door neighbor's house.
While police have not determined the cause or the motive for the fire, they have been able to rule out two possibilities. They say it was not caused because of a faulty electrical wiring or a bad space heater.
The victims' 4-year-old brother was brought to the Comer's Children's Hospital and the family said on Wednesday night that he is recovering.