Police announced they were reviewing CCTV images after illegal posters criticising the Pope's treatment of conservatives within the Catholic Church appeared in the Italian capital.
Dozens of the banners, which include a picture of the Pope frowning, have been discovered prompting council workers to swiftly cover them up.
They criticise the pontiff's intervention into a row involving contraception distribution programme linked to a lay Catholic order.
Unnamed sources in Rome suggest the posters could be the work of a far right group which is angry at the pontiff's support for immigration and refugees.
There's a rising anti-immigration feeling in Italy with increasing support for parties which oppose refugees.
The posters also accuse Pope Francis of "ignoring cardinals", an apparent reference to him effectively side-lining the conservative Cardinal Burke.
He publicly challenged the pope last year over his decision to ease Communion restrictions on divorcees who remarry outside the Church.
Fr Antonio Spadaro, a Jesuit who is close to the pontiff, said the posters illustrated how Francis was doing well in his role and therefore upsetting many people.