Chicago police said the boy fell just after 11 p.m. in the 1200 block of South Kildare Avenue.
According to the CPD, he broke his right ankle and Chicago firefighters took him to Stroger Hospital in good condition.
As of Thursday morning, no one was in custody.
The CPD said the incident is still under investigation by Site 4 detectives.
Authorities said the one-year-old boy was seriously injured after falling from a third-story window in the Englewood area earlier this month.
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