Crews were called about 6 a.m. to the blaze in the 9600 block of South Ewing, and it was upgraded to a second-alarm fire about 35 minutes later, according to the Chicago Fire Department.
One person was taken to a hospital in critical condition with severe burns, fire officials said. Another person was injured when they jumped from the building, and a third suffered minor cuts.
More than 100 emergency crews were called to the scene. Firefighters rescued two dogs from the building.
By the time the fire was brought under control about an hour later, the back of the building had collapsed. Witnesses said it shook at the start of the fire, indicating a possible explosion, officials said. The cause is under investigation.
