paris two french prison inmates soon free place investigation suspicion plan terrorist attack communicate smartphone syria stronghold islamic state militants news highlight risk regularly flag right group jail authorities crowd prisons offer fertile grind religious radicalization conversion cause islamist fighters france also prompt call crackdown use smartphones inside prisons two near end jail time hold-ups criminal activity terrorist offences take cells late last week interrogate four days place formally investigation suspect terrorist activity judiciary official say one element prompt authorities act interception encrypt message traffic syria fresnes prison staff representative cedric boyer say precise nature plan clear add convey seriousness perceive threat two constitute justice minister nicole belloubet tell europe radio happen yesterday expose urgency situation french tv station lci say two plot attack jail wardens police force source close investigation say also target plan 240 people kill france attack since start 2015 assailants pledge allegiance inspire islamic state france long record radicalization prisons prison guard say ease smartphones use communicate secretively world outside increase problem government go put hand pocket say boyer representative force ouvriere labor union guard fresnes prison extra staff need also matter keep technology able scramble 4g communications rather stay stick age nokia 33-10 boyer tell bfm tv refer late technology days mobile phone rudimentary novelty soon-to-go-free jail convict snare french attack plot probe