Switzerland’s Federal Intelligence Service said Monday it will allow access to a long-sealed file on Nazi war criminal Josef Mengele, potentially shedding light on whether the Auschwitz doctor hid in or passed through Switzerland after World War II.

The move reverses a February 2026 decision denying access to the file. Swiss officials said the change came after confirming it had already been reviewed by the Bergier Commission, which investigated Switzerland’s actions during World War II. Under a 2001 government ruling, such files are meant to be opened under more lenient access rules. “The appellant will thus obtain access to the file under conditions and modalities still to be defined,” the Federal Intelligence Service said.

The appeal was brought by Bern historian Gérard Wettstein, who has been seeking access to the file through the Federal Administrative Court. His central question is whether Mengele was in Kloten, near Zurich, in 1961, and whether Swiss authorities failed to arrest one of the world’s most wanted Nazi fugitives.

Mengele, known as the “Angel of Death,” served as an SS doctor at Auschwitz, where he carried out selections and brutal medical experiments, especially on twins. After the war, he fled Europe, lived for years in South America, and died in Brazil in 1979 without facing trial.

The file, transferred to the Swiss Federal Archives in 2001, was previously expected to remain sealed until 2071 because the last documents were added in 1991, restarting an 80-year protection period. Its opening could now provide long-awaited answers about whether Switzerland was part of one of the most infamous Nazi escape routes.