Agent says Mossad located Nazi war criminal as early as 1960, but he evaded capture and died in 1979.
Federal police agent holds two photos and the identity card June 7, 1985 found in the house in which the man believed to be Nazi War Criminal Josef Mengele lived.
"At the same time as we caught Eichmann, Mengele was living in Buenos Aires. We found his apartment and kept it under observation," he told Israeli public radio as the spy agency declassified its file on operations against the man known to prisoners as the "Angel of Death".
Yediot Aharonot newspaper, citing the newly available material, said that Mengele as chief medical officer at Auschwitz had "sent hundreds of thousands of Jews to the gas chambers with a wave of his hand".
The man police believe is Nazi war criminal Josef Mengele, third from right, poses for a photo during a picnic with friends in Sao Paulo, Brazil.
"He also directed shocking 'medical' experiments on prisoners," it wrote.
Eitan, 90, said that while the Mossad had Eichmann in a safe house ahead of smuggling him out of Buenos Aires in an El Al plane, the agency's chief, Issar Harel, wanted them to move against Mengele as well, but he argued against the plan.
"I didn't want to carry out two operations at the same time because we had one successful operation in the bag, and in my experience if you try to carry out another one you put them both at risk," Eitan said.
"At the end of 1962 Mengele was positively identified at a farm near Sao Paulo."
Yediot's Ronen Bergman told Israeli army radio in an interview that the Mossad files revealed some embarrassing slips, such operatives looking for Mengele "for a large part of the time in Paraguay when in fact he wasn't there," but actually in Brazil.
He wrote in the paper that there was also a costly 1983 operation in West Berlin to bug and follow Mengele's son Rolf in the hope that he would lead agents to his father.
Mossad also deployed an "intelligent and attractive" female agent posing as a private secretary to try and get close to Rolf and pry information from him, he wrote, but without success.
He quoted the Mossad archive as listing another plan, not implemented, where a caller claiming to be a close friend of Mengele would call Rolf and tell him that his father was gravely ill and he should go to him at once.
His death was only confirmed in 1985, after his body was exhumed.