WARSAW, Poland (AP) — Vandals have desecrated a monument marking the spot in Poland where hundreds of Jews were burned alive during World War II, scrawling "they were flammable" and a swastika on the memorial.

The monument in the town of Jedwabne honors the victims of July 10, 1941, when about 40 Poles hunted down Jews, closed them in a barn and set it alight. Between 300 and 400 Jews were killed in one of the better known cases of local people collaborating with the Nazis in killing Jews during the Nazis’ wartime occupation of much of Eastern Europe.

The vandals used green paint to spray the symbols of a swastika and "SS" — the name of an elite Nazi force — on the monument, as well as the phrases "I don’t apologize for Jedwabne" and "they were flammable."

Police discovered the desecration Wednesday during a patrol and are trying to find the culprits.

The massacre was unknown for decades but came to light with the 2000 book "Neighbors: The Destruction of the Jewish Community in Jedwabne, Poland," which sparked outrage and soul-searching in Poland.

It led to a government investigation that confirmed that Poles — and not Nazi Germans — were to blame for the killings. Poland’s then-president Aleksander Kwasniewski apologized for his country’s sins, but some Poles today remain in denial that such horrors were committed by their own people.

Meanwhile, Polish officials on Thursday were commemorating the anniversary of the German attack on Poland on Sept. 1, 1939, that marked the start of World War II.