In a press release Monday, officials from the shrine announced that in the early hours of Sunday morning, four statutes on the sides of the church as well as the church itself were painted with graffiti.
In the John Paul II Plaza, statutes of Popes John Paul II and Paul VI were painted. In the Pius XII Plaza, statues of Pope Pius XII and Bishop José Alves Correia da Silva were painted.
The graffiti includes the words "Islam," "moon," "sun," "Muslim" and "mosque."
According to the statement from shrine officials, "the difficult work of cleaning" is under way.
The communiqué added: "In reporting what has happened and without knowing who has done this, the shrine [officials] confirm [our] sadness and assure that the issue has been reported to the police."