The dead included two young brothers -- a 3-day-old and a 3-year-old.
Officials said Monday night they may never know what caused the blaze at the three-story apartment.
The early Sunday morning fire gutted the apartment building. The death toll rose throughout the day as investigators combed through the remains.
Family members who lost loved ones in the fire grieved on Monday.
"I wish I could have went up there and saved them, but I couldn't get up there because the flames were too high," said Allison Gist, mother and grandmother of victims.
"When I woke up, I heard someone yell 'fire' and there was nothing else I could do," said Elijah Grays, father and grandfather of victims.
Even with the support of his brother, Grays is a man devastated by tragedy after fire claimed the lives of five of his family members.
"It's hard to accept this at the moment. I've lost three kids and two grandkids, her boyfriend and another friend of the family. Right now, I'm just hurting inside," said Grays.
Grays said his 18-year-old daughter, Sallie Gist, her boyfriend, 20-year-old Byron Reed, their sons, 3-year-old Rayshawn and newborn, 3-day-old Bryon, perished in the blaze. Family friend, Tiera Davidson, 19, along with Grays' 16-year-old twins, Elicia and Elijah, also died.
"By the time we got to the front, the mom and dad were there saying that the two twins were in there up there still," said Peter Molina, fire victim.
Molina and his mother, Connie Rodriguez, neighbors of the victims, were left homeless by the flames. They now call a local motel home.
Fire investigators say damage to the building was so severe they have been unable to determine what caused the fire and have ruled nothing out. They believed it started in the back patio area and traveled up to the attic.
"The fire was coming through all the windows. The roof was caving in. There was mayhem," said Ted Kolin, Cicero assistant fire marshal.
The fatal fire struck the family's west suburban Cicero apartment early Valentine's Day morning as the family planned to celebrate Grays' birthday.
"I made everyone get out. Everybody was getting out and I opened the door to the attic, which is upstairs, like in the third story, and they were trapped up there. There was no other way up and no way down," said Grays.
All of the children's remains were found in the attic. The two other adult victims were found on the back staircase.
Twenty to 30 people may have lived in the building's four units, prompting authorities to review the building's codes and raising questions about overcrowding in apartments in Cicero.
"We will look at the history of the owner, any other buildings they have. We're not saying he did anything wrong," said Ray Hanania, Cicero spokesman.
Three firefighters were injured; one was still in critical condition Monday morning.
The victims' bodies were burned beyond recognition and family members were unable to identify them at the medical examiner's office.
Rev. Debra Williams is trying to keep the victims' family members going.
"There are no words to cover and provide what's needed. But we have even been able to laugh a little bit as we reminisce and keep encouraging them, that's all," said Rev. Williams.
Fire officials say that there were working smoke detectors inside the building at the time of the fire.
Investigators trying to determine cause
As the families of the victims grieved Monday, investigators were back working at the scene of the fire trying to determine how it started. They are also trying to determine how many people lived in the apartment building and whether any occupancy codes were violated.
The belief is the fire started in a rear porch area, but that section of the house was reduced to ashes so determining how it started won't be easy.
"We'll come pretty darn close. We're sifting now right through it. We have the best people. If we can come up with something, we'll come up with something," said Ron Opalecky, Cicero assistant fire marshal.
Investigators are looking at everything -- mechanical and electrical. They have no reason to believe the fire was set, but haven't ruled anything out.
There were four apartments in the building on the first and second floors. But five of the seven victims -- including the two youngest -- died in the attic which had been converted into living quarters.
"There were four mailboxes on the building, but it sounds like there were five units. That's something we need to look at to determine what is true and not true," said Hanania.
Cicero town officials say it is very early in what they promise will be a comprehensive investigation. Existing code though says that every dwelling unit shall have two safe, unobstructed means of egress leading to safe and open space at ground level. The attic living quarters had only a single stairwell, and it was blocked by fire.
Lorraine Santana, who lived on the second floor, says she was concerned with so many people living in the building.
"I did make out a few reports and did call it in, but every time it was checked out, I mean nobody was home. They come and they check and no one is home, so to me it was a concern," said Santana.
When homes are bought and sold, there are typically required affidavits specifying how many permanent residents there are.
"Once somebody takes occupancy, it's very difficult to inspect. People have rights, and they exercise those rights. But we're going to pull those documents and review those documents," said Dennis Raleigh, Cicero town trustee.