Four people were hurt overnight when a railing gave way on a crowded second-story staircase in Calumet Park.
Ten people were packed onto the stairs when the metal rail broke apart, authorities said.
Two of the victims were still unconscious when paramedics arrived.
Village officials planned to inspect the entire apartment complex Tuesday.
Firefighters have blocked off the second floor in the building where the bannister fell, he said. Building inspectors have also blocked off stairways in the two buildings that were not affected.