The head of the Sicilian Mafia, Bernardo Provenzano, has been put under tighter security amid suspicion that he is directing the mob from his cell.
Mr Provenzano was arrested in April 2006
Italian prison guards say they suspect he was using his Bible to communicate in code with his men on the outside.
Provenzano was arrested in 2006 after 43 years on the run.
During that time the Cosa Nostra boss had shunned all normal methods of communication, other than coded messages on pieces of paper.
FBI code-breakers brought into help think they were encrypted using a mysterious system of biblical references.
The Bible found in Provenzano's isolated hut at the time of his arrest in 2006 contained dots, arrows and notations.
Communication cut off
Provenzano is subject to the tightest surveillance at the high security Novara prison in Piedmont, northern Italy.
Under rule 41 - the law which governs the imprisonment of Mafia bosses - he is held in permanent isolation.
His letters, his phone calls and any permitted visits are closely monitored.
And yet it appears that the so-called Godfather still exerts his influence over the operations of the Cosa Nostra, the BBC's Christian Fraser in Rome says.
Police think he is communicating via his Bible which he had been given according to basic human rights.
The prison authorities say they are now cutting off all Provenzano's communication, partly to improve morale within the prison where inmates believe he is still in control.
After his arrest Provenzano was believed to have handed the reins of the Cosa Nostra to a younger man, Salvatore Lo Piccolo.
He was arrested in November and police are still not sure where the mantle boss of bosses now lies.