UPDATED 08/29/11 12:53 p.m.
CHICAGO (CBS) -- The cause remains under investigation Monday for a fire that left 100 people homeless and injured a firefighter in the Boystown neighborhood over the weekend.
The cause of the fire was not known as of the latest reports.
"We have no idea what started it," Fire Media Chief Kevin MacGregor said Saturday night.
The first calls about the fire were around 1:45 p.m., and about an hour later, the fire had been upgraded to a 3-11 alarm, MacGregor said Saturday.
Fire officials said the flames spread up the stairway, into the third floor apartments and from there to the space between the ceiling and roof, making the fire more difficult to extinguish.
The buildings lacked any rear exit aside from the area near the stairway. As a result, firefighters had to go around the block if moved from front to back, instead of through the building, wearing them out more quickly and prompting the 3-11 alarm.
Residents were able to escape without injury. But a firefighter was treated for a shoulder injury at Advocate Illinois Masonic Medical Center.
One resident of the building, named Ivanna, said she did not hear any fire alarm, only a commotion outside her second-floor window. When she looked outside and saw people running half-clothed with their belongings, she dressed, grabbed her wallet and ran outside.
Following the fire, many people crowded onto the intersection of Cornelia Avenue and Fremont Street, many tearful and agitated as they wondered when they could go back to the building, the Chicago Tribune reported.
About 100 people were displaced by the blaze, since about 60 units were affected, according to the American Red Cross. Most of the residents who were displaced have been able to find temporary shelter with family, a Red Cross spokeswoman said.
The buildings are located on a quiet block about half a block west of the Hydrate bar and Caribou Coffee shop on the Boystown strip of Halsted Street.
The offices of Grab Magazine, a local gay publication, were destroyed in the fire, the magazine confirmed on its Twitter feed.
The Windy City Times reported that Grab publisher Stacy Bridges operated and published the magazine from his home.
The Boystown Facebook page said the fire should serve as a reminder to consider renters' insurance.
"A common thing for people to say is that 'I'm always careful' or 'nothing like that is going to happen to me.' And then BOOM, the water heater bursts and your macbook, your iPad, your designer clothes are all damaged. Did you know, your landlord is not responsible for damages when that happens?" the administrators for the page wrote Sunday.
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