Stuttgart  - A German state set out plans Tuesday to jam wireless-phone calls from inside prisons, after admitting that tiny cellphones were being routinely smuggled into jails by visitors.

The Justice Ministry of Baden-Wuerttemberg state said prisoners were using the phones to direct criminal activities outside or plan their escapes. Though private phones are prohibited, they are still being brought in, often concealed in cakes or in bodies.

Jammer radio signals at a jail mean only crackly static will be audible on mobile phones inside the prison perimeter in future.

Special legislation authorizing the jamming was approved by the state government Tuesday and will be submitted to the state assembly.