VATICAN CITY (Reuters) - A Vatican judge on Tuesday ordered an investigation of the Holy See's police force after Pope Benedict's former butler said he was held in a tiny room with the light on constantly for the first few weeks of his detention.

The judge ordered the investigation after Paolo Gabriele and his lawyer made the assertions on the second day of the trial where he is accused of aggravated theft.

Gabriele, who is on trial for stealing papal documents alleging corruption in the Vatican and leaking them to the media, said he did not have any direct accomplices but was influenced by others and by widespread malaise in the Vatican.

(Reporting By Philip Pullella and Naomi O'Leary)