A report said that criminals are increasingly using drones for contraband smuggling.
Prisoners or their friends from the outside are increasingly using drones to smuggle contraband like drugs and pornography into federal prisons, USA Today reported on Friday.
Documents obtained through open record requests show that criminals have conducted nearly a dozen prison smuggling operations using drones over the past five years.
Get Data Sheet, Fortune’s technology newsletter.
Federal prisons in California, Louisiana, and Texas were among those targeted. USA Today did not provide details about each smuggling attempt, but it noted that several of the incidents involved using drones to covertly carry mobile phones.
A jail management consultant quoted in the report explained that drones present another way for prisoners to sneak contraband into penitentiaries in addition to more conventional means like bribing prison staff or hiding goods inside their bodies.
The rise of drones for smugglings add to the risk of criminals sneaking more deadly items into prisons like guns, the consultant said. USA Today did not specify whether anyone has been able to successfully sneak in weapons by using drones.
For more on technology and finance, watch:
It’s not just U.S. prisoners who are using drones for smuggling. A BBC report published in 2016, also based on a government records’ request, that prisoners tried at least 33 times to smuggle contraband into U.K. prisons.