Pope Benedict has met with three retired cardinals who are carrying out a probe into a leaked-documents scandal that revealed a power struggle in the highest levels of the church hierarchy.

The closed-door meeting with Spaniard Julian Herranz, Jozef Tomko of Slovakia and Italian Salvatore De Giorgi was scheduled for Saturday afternoon. No other information was available.

The scandal broke in January when Italian journalist Gianluigi Nuzzi revealed letters from a former top Vatican administrator who begged the pope not to transfer him for having exposed alleged corruption that cost the Holy See millions of dollars. The prelate (Archbishop Carlo Maria Vigano) was transferred and is now the Vatican's ambassador in Washington.

Last month Nuzzi published an entire book based on new documentation, including the pope's personal correspondence with his private secretary.

The pope's butler Paolo Gabriele was arrested May 23 and charged with stealing papal documents found inside his Vatican City apartment.

But Italian news reports quoted Vatican sources as saying the butler could not have acted alone and was possibly acting on behalf of more powerful figures.

The investigative panel headed by the three elderly cardinals has a broad mandate to question Vatican officials and prelates to get to the bottom of the leaks.