A Wikipedia article describing a World War II Nazi death camp in Warsaw in which large numbers of Poles were gassed was full of falsehoods and may have been the online encyclopedia’s most enduring hoax before it was rewritten in August, an Israeli newspaper has established.

The false Wikipedia article on the “Warsaw Concentration Camp” said the facility contained gas chambers and that 200,000 people died there. Both claims are unfounded, yet they remained on the English-language Wikipedia page for most of the last 15 years, the Haaretz daily reported Friday.

The erroneous article was translated into a dozen other languages and the false claims made their way into other Wikipedia articles, garnering over 500,000 views in English.

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There is a kernel of truth to the claims — there was a group of internment centers around the same location during the war, but it was a far cry from the “extermination camp” described in the misleading entry. The existence of the actual internment centers likely helped provide cover for the false claims, the Haaretz report said. The Wikipedia article had also claimed that the camp’s files were burned and its gas chambers blown up, leaving little evidence. Between 4,000 and 20,000 people actually died at the KL Warschau camps.

The Wikipedia page now contains a section on what it describes as the conspiracy theory surrounding the internment camps.

“There is no historical evidence of German gas chambers ever existing in Warsaw, and nowhere near 200,000 people died in the cluster of Nazi internment centers that did stand at the basis of the myth of KL Warschau,” Haaretz noted. It quoted Tel Aviv University’s Prof. Havi Dreifuss, a Yad Vashem expert on Poland and the Holocaust, curtly dismissing the claim of Nazi gas chambers in Warsaw as “fake history.”

Haaretz said its investigation of the false article uncovered a much wider problem — a concerted effort by Polish nationalists to alter hundreds of entries on the site to improve Poland’s wartime reputation.

The effort is part of a larger trend in Poland to distance itself from culpability in the Holocaust and portray the Polish people solely as victims of Nazi persecution, despite growing research on the depth of Polish complicity in Nazi crimes.

Politicians from Israel and Poland have long been at odds over Warsaw’s stance toward the genocide.

Warsaw has also long been at pains to state that Poland as a nation did not collaborate in the Holocaust, although individual Poles committed what the Polish ambassador to Israel described as “abominable crimes.”

Israel and Poland have seen diplomatic tensions over Polish officials’ rejection of any culpability by the nation for anti-Semitic atrocities of the past. Last year, the government introduced a controversial law that forbids blaming the Polish nation for Nazi crimes (though the legislation was softened following Israeli pressure to remove punitive measures).

The ruling Law and Justice Party has also campaigned heavily against Jewish Holocaust restitution claims, leading Jewish leaders to warn the debate had turned anti-Semitic. In May, thousands of Polish nationalists marched to the US Embassy to protest US pressure on Poland to compensate Jews whose families lost property during the Holocaust. It appeared to be one of the largest anti-Jewish street demonstrations in recent times.