Berlin police say they're investigating the disappearance in the German capital of more than a half-dozen "stumbling stones" — small brass plaques placed in the sidewalks outside of the former homes of Jews and other victims of the Nazis.

Police said Monday that residents in the central Neukoelln district reported the small memorials missing from several streets.

The project was initiated in 1996 by artist Gunter Demnig, and seeks to bring back the names of Jews and others to places where they once lived. Each square plaque carries the name of the victim and information like when they were deported and where they were killed.

Demnig says on his website that more than 60,000 of the plaques have been installed across Europe.