BERLIN — 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 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 October 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.

Germany opened the long-awaited memorial in 2012. Designed by Israeli artist Dani Karavan, it features a water-filled basin with a retractable, triangle-shaped column at its center that is topped by a fresh flower every day.

Panels detailing the Nazis’ persecution of the minority surround the memorial, which is located across the road from the Reichstag, Germany’s Parliament building, and close to memorials to the Nazis’ Jewish and gay victims that have been inaugurated in recent years.

Roma were subjected to racial discrimination from the early days of Nazi rule. Before Berlin hosted the 1936 Olympic games, hundreds were rounded up and interned; and in 1938, SS chief Heinrich Himmler set up a central office for the persecution of the Roma people.

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

Their fate drew little attention as post-World War II Germany began to come to terms with the Nazis’ crimes, primarily focusing on the slaughter of 6 million Jews.

Only in 1982 did West German Chancellor Helmut Schmidt publicly declare that Sinti and Roma “were persecuted for reasons of race. These crimes constituted an act of genocide.”