(ANSA) - Vatican City, October 2 - Pope Benedict XVI's former butler Paolo Gabriele pleaded innocent on Tuesday to stealing confidential Vatican papers. But he said he felt guilty of betraying the pope's trust. Gabriele told a Vatican court that he thought the pontiff was being manipulated. "Over time I became convinced it was easy to manipulate a person who has such enormous decisional power," he said. "Sometimes... the pope asked questions about things he should have been informed of". Gabriele added that other people have leaked sensitive Church documents to the press as well as him. "I wasn't the only one in recent years to provide documents to the press," he said. But when it came to the crimes he is accused of, Gabriele said he "absolutely did not have accomplices". Gabriele's arrest on May 25 rocked the Catholic world after months of sensitive Church correspondences surfacing in the Italian media. The leaked documents included letters to the pope and Vatican Secretary of State Tarcisio Bertone from the Holy See's ambassador in Washington, Carlo Maria Vigano, who was deputy governor of Vatican City at the time they were written. The letters contained allegations of corruption in the management of Vatican City. The Vatican has blasted the media's coverage of the leaks affair and Bertone has accused journalists of playing at being Dan Brown, saying they were guilty of "inventing tales and peddling legends". Following complaints from Gabriele regarding his treatment behind bars, the Vatican on Tuesday opened an investigation into his detention conditions. According to Gabriele, he "couldn't even open his arms" in the first cell where he was first detained following his arrest, adding that for the first 15-20 days the lights were always left on. "There was no light switch," Gabriele told the court. "The light was on 24 hours a day and this has also led to a reduction in my eyesight". He added that on the first night he was subjected to pressure and also denied a pillow. Vatican spokesman Father Federico Lombardi said that the probe had been opened to verify possible violations in Gabriele's treatment, but also to establish "whether there have been unfair accusations against the judicial authorities". Lombardi described the defendant's detention conditions as "very humane" and said that even the smaller cell in which he was originally detained "respected international standards". Meanwhile the Vatican Gendarmerie said in a statement that Gabriele had received "special attention" during his detention and that the light had been left on for security reasons and to prevent possible incidents of self-injury by the prisoner. The Vatican police corps also said that Gabriele could be liable to a counter-suit should the charges be ruled unfounded.