VATICAN CITY — Pope Benedict XVI's butler risks up to six years in prison if convicted on a charge of aggravated theft for stealing classified documents from the papal chambers, a Vatican judge said Tuesday.

Paolo Gabriele, a staunch Catholic who is seen as the layperson with the most access to the Vatican's corridors of power, was caught last month in possession of the documents in his home and is being detained in the Holy See.

The 46-year-old, whose lawyer says he is ready to cooperate with the inquiry, was formally questioned on Tuesday for the first time before a judge with his lawyers present and is awaiting a ruling on whether he will stand trial.

The unprecedented inquiry has been kept under close wraps by the Vatican but Italian media have reported that the inquiry could extend much further than Gabriele and that a fierce behind-the-scenes power struggle is under way.

Gabriele's current charge carries a sentence of between one and six years. The Vatican's criminal code also contains charges such as offence against the sovereign, receiving stolen goods and revealing state secrets.

Judge Paolo Papanti-Pellier, who is not currently involved in the case, told reporters that Gabriele would be tried in the Vatican if the trial goes ahead but could not then be imprisoned there as the Holy See has no prison.

"If the defendant is convicted, the Vatican would make a request to the Italian government for him to serve out his sentence in an Italian prison" under the Lateran Pacts signed by Italy and the Vatican in 1929, he said.

The judge said Gabriele was currently being held in a 16 square metre (170 square foot) Vatican "security room" decorated only with a crucifix.

He said Gabriele had been allowed to attend mass on Sunday in a church in the Vatican accompanied by two officers but without wearing handcuffs.

The judge said the Vatican's criminal code was based on the one in force in the then Kingdom of Italy in 1889 and was relatively lenient. He added that the pope could issue a pardon at any stage of the investigation or trial.

Documents allegedly stolen by Gabriele, including sensitive memos about the Catholic Church's handling of child abuse scandals and of accusations of money laundering, have been published by Italian newspapers and in a book.

Some Vatican watchers say Gabriele may have been acting with others to defend the pope against an overly powerful entourage, while others say he may have been helping to prepare the way for a new Italian pope to succeed Benedict.