Switzerland's Federal Intelligence Service has made public a secret 200-page dossier detailing the post-war movements of infamous Nazi war criminal Josef Mengele in the country.
The documents, released on Thursday, September 10, were previously locked in Swiss archives under a protective embargo scheduled to last until the end of 2071.
The newly published records shed light on a long-standing historical mystery regarding how closely the SS doctor was connected to Switzerland while fleeing international justice after World War II.
Alpine holiday under a false identity
The dossier confirms that Mengele traveled to Switzerland in 1956, roughly a decade after the fall of the Nazi regime, while living in South America under the alias Helmut Gregor.
He entered the country by traveling from South America through New York to Geneva before heading to Engelberg, a prominent winter resort in the Swiss Alps.
Mengele spent approximately ten days skiing and vacationing at the resort alongside members of his family, including his young son Rolf.
Rolf did not know that the man was his father, as Mengele introduced himself as Uncle Fritz while the child believed his real father had gone missing in the war.
The presence of one of the world's most wanted war criminals at a popular Swiss tourist resort went entirely undetected by local authorities at the time.
Investigation near Zurich in 1961
Five years after his Alpine trip, Swiss authorities launched an investigation into reports that Mengele had returned to the country in 1961, specifically in Kloten near Zurich.
The inquiry was triggered by the presence of his wife, Martha, in the area, raising concerns that the fugitive had secretly re-entered Switzerland to meet his family.
Suspicions intensified following reports of an unidentified man seen near Kloten, though surviving records do not prove that the individual was Mengele.
The investigation gained widespread attention after a reporter for the German newspaper Bild claimed to have spotted Mengele inside a Kloten apartment.
Police investigators subsequently established that the journalist had been monitoring the wrong apartment, though the incident remained a primary reason historians sought access to the file.
Instructions for immediate arrest
The newly declassified files reveal that Swiss police were actively preparing for the possibility of catching the fugitive doctor on Swiss soil.
Zurich cantonal police requested formal permission from federal officials to arrest Mengele immediately if he was identified within their jurisdiction.
Although West Germany had not yet issued a formal extradition request at that time, officials in Bern instructed Zurich police to place Mengele under provisional detention for extradition if located.
The directive undermines long-held theories that Swiss officials were aware of Mengele's presence in 1961 and deliberately allowed him to escape capture.
Auschwitz atrocities and escape
Josef Mengele served as an SS doctor at the Auschwitz extermination camp in Nazi-occupied Poland, where approximately 1.1 million people were murdered, including nearly one million Jews.
He became infamous for performing brutal medical experiments on prisoners and children under the guise of scientific research, showing a particular interest in twins used in fatal procedures.
Following the collapse of the Third Reich, Mengele escaped Europe using forged identity documents and Red Cross travel papers to reach South America.
He evaded international law enforcement and Nazi hunters for decades by moving between several South American nations without being brought to trial.
Mengele drowned in Brazil in 1979 after suffering a medical emergency while swimming, though his death remained secret for years until his remains were identified.
Legal battle over classified records
The documents released this week were originally compiled by the police division of the Federal Prosecutor's Office, an institutional predecessor of the Federal Intelligence Service.
The files were transferred to the Swiss Federal Archives in 2001 and placed under an extended embargo set to expire at the end of 2071.
Swiss intelligence officials repeatedly rejected access requests from researchers citing source confidentiality and personal data protections, including a rejection issued in February 2026.
The policy changed after historian Gérard Wettstein, who was researching Mengele's activities in Switzerland, challenged the refusal before the Federal Administrative Court.
During court proceedings, officials discovered that the file had been examined by the independent Bergier Commission, which investigated Switzerland's role during World War II.
A 2001 Federal Council ruling mandated broader public access for documents reviewed by the Bergier Commission, but the Mengele dossier had lacked the internal cataloging markers needed to identify it.
The Federal Intelligence Service acknowledged that it had been unaware that the file fell under the 2001 disclosure rule until the recent court review.
Following a formal decision on September 8, the agency uploaded the approximately 200 pages of documents to the internet on September 10.
Redactions and remaining mysteries
The public release of the dossier includes specific redactions designed to protect intelligence sources, personal data of third parties, and details concerning current and former officials.
Intelligence agency officials stated that redactions were kept strictly to what was necessary and that the narrative of events recorded in the files remains clear.
The original, unredacted master file remains preserved within the holdings of the Swiss Federal Archives.
While the release clarifies Mengele's 1956 trip and the 1961 police response, it highlights the efforts of authorities to track a war criminal who ultimately died without facing a court.
