Investigators have determined a cause of the fire that led to the deaths of two firefighters Wednesday.
The Chicago Fire Department Office of Fire Investigation announced Friday that the fire was sparked by an "open flame ignition of ordinary combustibles / wood/ rubbish."
The fire broke out in the rear portion of the building at 1744 E 75th St
Corey Ankum, 34, and Edward Stringer, 47, died and more than a dozen other firefighters were injured when the building collapsed. Both men died while searching for people inside the building.
Gas and electric service had been off for many months, investigators said.
The building use to house a dry cleaning business but has been vacant for the last five years, becoming a favorite spot for homeless people seeking shelter from the winter weather.
The Chicago Police Department takes over the investigation at this point and will determine is there was any criminal intent.
NBC Chicago caught up with several firefighters at a Pilsen store Friday who were getting new uniforms for the upcoming funerals. Some had casts on their legs and stitches in their heads after surviving the roof collapse.
T.C. Britton was supposed to be Ankum's relief that day.
"It's really sad. When I see him on TV, I feel like he's looking at me thinking 'where's my relief at?'" Britton said.
Ankum had been on the force for nearly two years and Stringer was a 12-year veteran.
Stringer's visitation will be held Monday at Blake Lamb Funeral Home in Oak Lawn and the funeral mass will be held Tueday at St. Rita of Cascia Chapel in Chicago. Arrangements for Ankum are still being made.