CHICAGO (CBS) — Investigators are trying to determine what cause a three-alarm fire that damaged four apartment buildings Tuesday in the Lawndale neighborhood on the West Side.

No one was hurt in the quick-spreading fire, which apparently began about 4:30 p.m. on the back porch of a brick three-flat at 4153 W. 21st Pl., said Fire Department spokesman Joe Roccasalva.

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The fire was already beginning to spread to the back porches of buildings on either side when the first firefighters arrived. Roccasalva said that prompted the call for a second alarm.

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

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.

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In all, approximately 125 firefighters battled the flames.