Police believe a 12-year-old child started the fire. He was possibly playing with a lighter.
The fire triggered a massive response. Hundreds of people lost everything as they watched the flames spread, tearing through three large buildings in the 800-block of McIntosh Court. Officials said 96 units were destroyed.
Residents have returned to the buildings throughout the day to try to recovery any of their possessions that may remain.
Barb and Paul Sagan were overjoyed to find their pet guinea pigs Lola and Angel had been rescued from the fire.
"I can't believe it. I can't. Our unit was in the worst spot," Paul Sagan said.
The fire investigation is still underway. Fire officials said it started in a single unit.
The damage is heartbreaking. Families left with nothing, trying to figure out how to rebuild their lives.
"I've lived here for 14 years and I can't believe this happened. Thank God we got my cat out," said fire victim Frank Kukla.
Fire victim Everardo Hernandez has nothing left but the clothes on his back, even losing his beloved cat to the smoke and flames.
"Now everything is gone," he said.
Jonathan Alvarez and his family, now homeless, are just hoping for a night without tears.
"I've got a 6-year-old daughter and she's devastated. It was hard for me to put her to bed last night. She kept on crying," he said.
Emotions ran high as residents confronted the Prospect Heights Fire Chief Thursday morning. Many were upset that the fire burned for so long and were upset over the preliminary cause of the fire.
"Kids play with things all the time and that's basically what we're trying to get to the bottom of whether or not there was any intent and I'm not prepared to comment. It looks accidental at this time," said Prospect Heights Police Chief Al Steffens.
The hollowed-out design of the roof allowed the flames to spread unpredictably.
Officials said three people suffered minor injuries, including a firefighter. They are all expected to be OK.
Because of its age, the 50-year-old complex was not required to have sprinklers.
A small flareup Thursday night forced firefighters to return to the complex. Most residents will not be allowed to return to see what of their possessions may remain until all buildings are deemed safe.
LOCAL CHURCH, RED CROSS, NEIGHBORS ASSIST FIRE VICTIMS
Lakewood Chapel in Arlington Heights and the Red Cross are working together to help hundreds of residents and their families who were forced out of their homes. The Red Cross had 100 cots delivered to the shelter at the church. They were also assisting with food and water.
"We believe in helping whoever struggles. That's the kind of church we are anyway," said Lakewood Chapel Pastor John Elleson.
The sanctuary at Lakewood Chapel has been transformed into a shelter for some of the hundreds of people who have been displaced. The Red Cross donated 70 to 100 cots for people.
Some displaced residents had to go to work Thursday, while others simply tried to figure out the next step.
"We don't have anything. We don't have a passport. Everything is inside the house," said 16-year-old Asael Villa.
While people who slept at the chapel Wednesday night are hoping to find a more permanent shelter, the pastor says they can come back here for as long as they need to.
They are also offering food, counseling, and assistance from the Red Cross on how to navigate the quagmire of insurance and what to do next.
Many area restaurants are donating food for the folks who will be staying there.
Other residents are donating clothing, baby food, all of the essentials you don't think about when you have them. Of course, when something like this occurs and it's all gone, you don't know where to start.
There are also comfort dogs present to help people who are having emotional difficulty.