Historians at the Auschwitz memorial and high-school officials in central Poland are trying to determine how a list of 15 Polish and Jewish inmates of the Nazi death camp made it into a school library book.

A typewritten page, stained and with edges burnt, was found last month inside a 1923 Polish book on the history of warfare, during a library stock-taking at the 2nd Lyceum in Lodz, some 200 kilometres from the former camp. “We have no idea how or when it came to be in this book,” school director Jadwiga Ochocka told the Associated Press (AP).

Auschwitz museum spokesman Pawel Sawicki commented that historians have no doubt it is authentic, but will still submit it to tests to confirm that. Sawicki said the find is all the more precious for the fact that the Nazis burned most of Auschwitz’s archives when they were readying to evacuate the camp in January 1945. Dated 21 May 1941, it bears the names of inmates brought to Auschwitz that day from Lodz, Poznan and Katowice. The same names are a longer list of 28 inmates brought in that day, which is held in the museum’s archives. According to historians, eight of the inmates on the list died in Auschwitz.