Investigators say Calogero Lo Piccolo had taken over his father's operations since the older man was arrested in early November, the Italian news agency ANSA reported.

Francesco Messineo, the prosecutor in Palermo, described the arrests as a major blow to La Cosa Nostra.

''Pockets of Mafia-controlled areas still exist but Cosa Nostra's power structure is reeling,'' he said. ''We have by no means defeated Mafia, however the extortion racket here has been dealt a major blow. Nevertheless, Cosa Nostra can still regroup as it has in the past.''

Salvatore Lo Piccolo is believed to have been the heir of Bernardo Provenzano, the alleged Mafia boss of bosses. When Lo Piccolo and another son were arrested Nov. 5, police found a cache of documents that included "pizzini" or messages from Provenzano.

Investigators say that decoding those documents provided valuable information that led to the new arrests.