The human remains were found about 10 a.m. Sept. 23 at the park at 2210 W. Pershing, according to Chicago Police.
A Chicago Park District worker found the bag during a routine clean-up, a source said.
The remains of the person found were described as black, between 15 and 25 years old, police said. Investigators are unsure if they were male or female.
Police have drained the lagoon to look for further body parts.
Anyone with information on the person’s identity is asked to call police at (312) 747-8730.
—Chicago Sun-Times Wire