The boy was taken to a local hospital Saturday after he was seen chewing on the foil in a house on West 5th avenue and started "acting lethargic," the Chicago Tribune reported.
The hospital called police to report a case of child abuse after tests for the drugs came back positive, the newspaper said.
Investigators searched the child's home and found drug paraphernalia, police said.
No announcement was made about possible charges pending in the case.
The child was listed in good condition in the hospital where he remained for observation, the Tribune reported.
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