The Chicago Fire Department continued to battle hot spots after a massive fire destroyed a North Side strip mall Friday.
Firefighters returned to the scene around 3:30 a.m. Saturday and were working to put out rekindled hot spots for about an hour.
They continued to work on hot spots as they sparked throughout Saturday.
"We'll probably still come back two or three times later," said Battalion Chief Michael Smandra. "We can't get to it because of the way the roof is caved in, for safety reasons."
Fire officials believe a roofing crew using propane torches sparked the massive blaze. Authorities say the roofing crew left after the fire started, and didn't return back to the scene.
NBC 5 reports that the roofers also left behind a vehicle at the strip mall.
It took emergency crews two hours to get the fire under control, which started at about 4 p.m.
Heavy smoke and flames could be seen pouring out of the building located at 3106 W. Peterson, near North Lincoln Avenue.
"It was a great business and beautiful store we built," said business owner Sammy Dajani. "It took 45 years to get to where we are at. Now it's gone, just like that."
The fire appeared to have originated at Mid American Furniture and then spread to the adjacent American Mattress store and a ForEyes optometry store.
A Supercuts and a nail salon are also located in the strip mall, and firefighters were also tasked with keeping the fire away from a liquor store, which could have created an even more flammable situation.
Nearby power lines caused several explosions at the scene.
Officials upgraded the incident to a four-alarm fire before it was struck, and used more than 200 firefighters to extinguish the flames.
The roof caved in on the building.
Firefighters set up on the north side of the burning building in order to prevent the fire from spreading to an apartment building directly behind the strip mall.
ComEd confirms 700 were without power on the North Side due to the fire.
The No. 11 Lincoln and the No. 84 Peterson CTA buses were also rerouted.
No injuries were reported at the scene.