Almost two-thirds of millennials and Gen Zers don’t know that 6 million Jews were killed in the Holocaust, and almost half can’t name a single concentration camp, an alarming new survey on Holocaust knowledge has found.

The survey demonstrated wide gaps in younger American’s knowledge of the genocide while also showing a concerning 15% of millennials and Gen Zers thought holding neo-Nazi views was acceptable.

“How much of that is based on genuine understanding of neo-Nazis principles and how much is based on ignorance is hard to tell. Either of them is very disturbing,” said Gideon Taylor, president of the Conference on Jewish Material Claims Against Germany, which commissioned the survey.

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“If people can’t name Auschwitz … that’s something that’s deeply concerning. I don’t think there is any greater symbol of man’s depravity in recent history than Auschwitz,” he added.

The survey is the fifth in a series that looks at people’s knowledge of Holocaust history worldwide as well as education around the genocide.

Read more: USA TODAY