But the case is proving to be a tough one to crack, with the chocolate treat's manufacturer, Ferrero, also the producer of Nutella, declaring itself the "wounded party" in the investigation.
The boy, from the town of Torrice, in Lazio, found the pill, used to treat hypertension, when he opened the egg in December.
Fortunately, his parents intervened before he could even contemplate eating the pill, and took the egg and its contents to the local police station.
An investigation was launched but food police still have no idea who put the pill inside the egg, or why, although they now suspect it was placed there deliberately.
“We're not ruling anything out but the evidence at the moment points to sabotage,” an investigator told La Repubblica.
Italy's food police were aided in their preliminary investigations by Ferrero, whose quality control department carefully monitors each stage of a Kinder egg's manufacturing process.
Ferrero said that the chocolate from the batch in question had been manufactured at a plant in the Piedmont town of Alba and that the gift capsule had been assembled in eastern Europe.
To add a further layer of mystery to proceedings, Zofenopril is only available in Italy.
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Nas are still trying to establish a motive and find a suspect at the eastern European plant with some sort of Italian connection.
For now, the case is an isolated incident.