Police believe they were set by someone igniting materials in garbage cans and alleys.
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The fires include one near 135th Street and Baltimore Avenue in the Hegewisch neighborhood Saturday.
Firefighters said when they arrived, a two-story building was engulfed in flames.
"You get awakened by all this activity and you come out and everything is burning, especially being in a news place," said Eric Outten, whose garage was burned. "It's quite disturbing."
Other buildings were also damaged when the flames spread. Four firefighters were transported to hospitals to be treated for minor injuries.
Police are looking at surveillance video for any possible suspects.
The other suspicious fires occurred in:
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13400-block of South Brandon Avenue, on July 6 at 4:50 a.m.
13100-block of South Burley Avenue, on July 8 at 10:30 p.m.
13400-block of South Baltimore Avenue, on July 11 at 5:50 a.m.
13400-block of South Burley Avenue, on July 12 at 8:15 a.m.
Anyone with information is asked to contact Chicago police arson detectives at (312) 746-7618.