Speaking to newspaper 20 Minuten, Rebecca de Silva, spokeswoman for a detention centre in Pöschwies, in the canton of Zurich, said there had already been two attempts to fly drones over the prison.
In both cases the drones were carrying no contraband but they should be “considered as experiments” and taken seriously, she said.
As a consequence, the prison is looking into ways to counter the practice, for example using radar, GPS or monitoring radio waves to detect drones, she said.
A prison in Menzingen, in the canton of Zug, is also looking to install a drone detection system after an unknown person succeeded in using a drone to deliver a mobile phone to an inmate two years ago, reported 20 Minuten.
Since then there have been no further recorded incidents but the prison's director, Andreas Gigon, told the paper he couldn't rule out that some may have gone undetected.
Some smaller prisons are considering putting nets over their exercise yards to defend against drones, said the paper, though that option is criticized by animal rights groups who fear nets would be harmful to birds.
The use of delivery drones for legitimate purposes hit the headlines in Switzerland last year when Swiss Post, the country's national postal service, began trialling parcel delivery by drone.
Earlier this month a company in the canton of Valais opened the country's first ever ‘drone pilot school' to train people how to operate the unmanned aircraft safely and within the rules.
While no authorization is required to fly drones of up to 30kg in Switzerland, certain rules and restrictions apply as to where and how they may be flown.