Nazi war criminal Josef Mengele was detained by the U.S. Army following World War II but was released months later because he could not be properly identified, according to notes and letters Mengele sent to his son.

The so-called "Angel of Death," who was responsible for the killing of 400,000 Jews at the Auschwitz concentration camp, avoided detection while he was detained because, for reasons of vanity, he had refused to tattoo his blood type in his armpit as all SS officers were required to do.

Allied investigators seeking SS personnel looked for the tattoo as a tell-tale mark in identifying high-ranking Nazi soldiers suspected of war crimes who might be put on trial.

When U.S. soldiers found no tattoo on Mengele and could not find any wrongdoing committed by a Fritz Hollmann -- the alias that Mengele was using at the time, he was discharged from the internment camp.

The revelations, which confirmed earlier reports that Mengele had been in U.S. hands after World War II, appeared in this week's edition of Bunte magazine, a Munich-based weekly that acquired from Mengele's son, Rolf, more than 30 pounds of notes, letters, and photographs illustrating Mengele's life on-the-run. Four historians who examined the materials have confirmed their authenticity.

The article was the second in a series Bunte plans to publish using excerpts from the papers and exclusive commentary from the younger Mengele to describe more than three decades of the fugitive-life in Europe and South America spent by the most-hunted Nazi war criminal. The magazine says it will donate all profits to the Auschwitz survivors' fund.

Last Friday, forensic scientists from Brazil, the United States and West Germany announced that they are convinced that the skeleton of a man buried as Wolfgang Gerhard and exhumed June 6 near Sao Paulo was that of Josef Mengele.

Mengele was avidly sought just after the end of the war by a team of Allied investigators seeking to put him on trial for his ghoulish experiments on twins, dwarfs and children at the Auschwitz concentration camp.

In a letter to his son quoted in the magazine this week, Mengele wrote, "At the war's end, my unit was in Czechoslovakia. On the night of the cease-fire, we pulled back to the west. In the vicinity of the nearest city, we were taken to a U.S. prisoner-of-war camp. We were transferred to many camps and then released in the American zone."

Mengele's son explained that his father was narcissistic and would stand for hours in front of a mirror admiring himself in hand-tailored suits. Rolf Mengele believes that his father's inordinate vanity made him flout SS rules and refuse to imprint his blood group under his arm.

After his release, Mengele returned to his hometown of Guenzburg in Bavaria but, fearing pursuit by would-be captors, took refuge in a nearby forest. In September 1945, two U.S. military officers questioned farmers in the Guenzburg region about Josef Mengele.

They also interrogated his first wife, Irene, who claimed she did not know where he was. She later divorced him, and Mengele married her sister, Martha, in 1958 in a Buenos Aires ceremony that was well-attended by Mengele family members and Nazi fugitives living in Argentina and Paraguay. Martha had been married previously to Mengele's brother.

The family reportedly delivered food supplies to Mengele at his forest hiding place before he moved to Rosenheim, also in Bavaria, where he worked as a stable groom. The owner said later he often wondered why the hired hand "spent so much time washing his hands."

Mengele stayed in Rosenheim until late 1948, when he made his way to Genoa to catch a boat to South America. In Genoa, Mengele was detained by Italian authorities who later apologized for mistakenly arresting him and let him proceed to Argentina.

Bunte said Mengele's writings proved that he maintained his enthusiasm for his Auschwitz pseudo-medical experiments that explored the possibilities of breeding a blond, blue-eyed superior race. The letters and notebooks show he made plans to resume his work and that he kept microscope slides with him of blood and tissue samples, apparently from Auschwitz, for the time when he could work in a laboratory.

Bunte's article is accompanied by numerous photographs of a skiing vacation in 1956, when Rolf Mengele met his father for the first time. Mengele was introduced as an uncle by the name of Helmut Gregor.

The pictures show the Mengele family cavorting in the snow in front of a hotel in Engelberg, and the magazine said it was evident that Mengele easily avoided capture and at the time felt no pressure of being pursued by German or Swiss authorities.