According to an investigation by the New York Times and German broadcaster ZDF last week, former SS doctor Aribert Heim had escaped to Egypt in the 1960s, where he converted to Islam and died in 1992 of cancer.
The Simon Wiesenthal Centre in Jerusalem said Wednesday that Egyptian authorities extended his residence permit in 1981 and a German embassy official had apparently registered his death.
"Research from ZDF (German TV) and the New York Times has shown that Heim lived for a long time in Egypt and it is highly likely officials from the German embassy knew about it," the centre's director Efraim Zuroff said. "How was it possible that Heim lived undisturbed in Egypt and received several visits from relatives?" Zuroff asked.
German and Austrian police said on Thursday after the ZDF and New York Times's findings were published that they were seeking to confirm that Heim had died and that they would hunt for his remains if necessary.
A spokesman for the German Foreign Ministry said on Wednesday Berlin was taking the issue "very seriously" and that there would be a "thorough investigation."
Finding his remains could be complicated because according to last week's report his body was disposed of in a paupers' grave where a large number of other corpses will have ended up in the intervening 17 years.
The Austrian-born Nazi became known as "Doctor Death" and the "Butcher of Mauthausen" after performing sadistic and grotesque medical experiments on concentration camp prisoners. He performed operations without anaesthetics and injected petrol directly into victims' hearts. His cruelty was such that he has frequently been compared to Josef Mengele, the so-called "Angel of Death" who was a doctor at Auschwitz.
In 1945 at the end of World War II he was arrested by the US military but they let him go after two and half years, and he went on to work as a gynaecologist in the picturesque spa town of Baden-Baden.
There he stayed for around 15 years. But his dark past caught up with him and Heim was forced to flee in 1962 just as the West German authorities were about to arrest him.
German TV showed an interview with Heim's son Rüdiger in which he said that his father was dead and that he had lived in Egypt. The journalists also found a dusty briefcase containing a haul of documents they said proved their thesis.