Pope Francis announced on Sunday that discussions are underway for the return of indigenous artifacts in the possession of the Vatican Museums.

He opened the door to returning other parts on a case-by-case basis.

“The seventh commandment comes to mind: if you steal something, you must return it,” the pope said during a press conference on his plane en route to the Holy See.

Francis recently returned to Greece the three sculpture fragments from the Parthenon that had been held by the Vatican Museums for two centuries. He said it was “the right thing to do” and that other museums should do the same, where possible.

This was his first public stance on an issue that has led many museums in Europe and North America to question their ethnographic and anthropological collections, amid growing awareness about the colonialism and as countries in Africa, America and Asia demand the return of their stolen artefacts.

The Vatican has an extensive collection of artifacts and works of art created by indigenous peoples from all over the world. Most of the objects were sent to Rome by Catholic missionaries for an exhibition in 1925.

The Vatican maintains that the artifacts, including ceremonial masks, wampums and feathered headdresses, were gifts. But indigenous researchers are questioning the real freedom of indigenous peoples to give away their creations, knowing the power relationship that existed during the colonial period.

Last year, Francis came to Canadian soil to personally apologize for abuses committed by Catholic missionaries in residential schools for Indigenous people.

Ahead of the papal visit, indigenous representatives visited the Anima Mundi Museum, spotted creations of their ancestors and expressed the wish to have better access to the collection and to have certain objects returned.

The Pope also repudiated the Doctrine of Discovery, which has been used to legitimize the taking of Indigenous territories and forms the basis of some property laws in Canada and the United States.