CHICAGO (CBS) — The cause remains under investigation for a fire that ripped through three apartment buildings in the Lawndale neighborhood.

As CBS 2’s Kris Habermehl reports, the fire broke out around 4:30 p.m. Tuesday on the back porch of a three-flat building at 4153 W. 21st Pl.

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By the time the first firefighters arrived, the flames had already spread to the back porches of the buildings on either side. A 2-11 alarm was called.

Fire officials said said the 98-degree heat prompted the call for a 3-11 alarm, because with heat nearing 100 degrees firefighters were circled in and out every 10 to 12 minutes, then allowed to rehydrate.

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By the time the fire was brought under control, about 40 minutes after the first alarm, the fire had gutted the three-flat in which it began. Flames had spread to the rear and top floor of the building at 4151 and 4155 W. 21st Pl., and to the porch of the building at 4149 W. 21st Pl.

By Wednesday morning, the fire was completely out and all the streets nearby were back open. But the porches collapsed and were completely destroyed, and the brick buildings in front of them sustained major damage.

The remains of the porches were left crumpled and charred in piles in ht rear of the property.

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The cause and origin of the fire remained under investigation Wednesday morning.