The drone, equipped with a camera, was able to navigate its way into the prison and pass through the helicopter net above the courtyard, according to a report by France Bleu.
It made its delivery at around 3pm on Tuesday, while the majority of inmates were outside in the Valence prison, located in the Drôme department of southeastern France.
The jail is reserved for prisoners serving long sentences, and saw two serious riots last winter when detainees stole a supervisor's keys.
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Guards raised the alarm immediately and carried out searches of the inmates, but were not able to recover the contents of its package.
The drone has been confiscated by police who are working to identify the sender and recipient.
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