Authorities say that a large swastika and the word "vergasen," or "to gas," were found daubed at Germany's memorial to the hundreds of thousands of Gypsies, or Roma, who were killed by the Nazis.

The foundation that oversees the memorial and others in Berlin commemorating Holocaust victims said Thursday that the vandalism was discovered at the entrance to the site on Oct. 16 and removed. It said it has stepped up security at the memorial, which is located in the Tiergarten park close to the Reichstag parliament building, and that police are investigating.

The memorial, with a water-filled basin at its center, was inaugurated three years ago.

It's not clear exactly how many Gypsies were killed during the Holocaust. Estimates range from 220,000 to more than 500,000.