Despite the installation of high-tech signal jammers, the use of mobile phones inside prisons continues to pose a challenge, the DG said. Officials have also found that some of the active SIM cards being used inside the prison were connections issued in Andhra Pradesh. The Prisons Department has sought details from the telecom operator and indicated that accountability would be fixed after verification of the subscriber information and the service provider will be booked . According to department data, nearly 300 mobile phones have been seized from prisons across Karnataka since the beginning of this year. Officials suspect that several more devices may still be operational inside prison premises despite repeated crackdowns.