Argentina ? The world’s top Nazi-hunter said Thursday he’s made progress in finding 94-year-old “Doctor Death,” a former concentration camp physician accused of torturing Jewish prisoners as they died and who may have been living for decades in Argentina or Chile.

Efraim Zuroff, head of the Israeli branch of the Simon Wiesenthal Center, said that his mission to the southern reaches of the Americas led him to at least four people who claim to have seen Aribert Heim in the past 45 days.

Zuroff launched the investigation last week in the southern Chilean fishing town of Puerto Montt, where Heim’s daughter lives, although she was reportedly overseas at the time.

Zuroff said during the past three years, Heim’s daughter has traveled several times to the Patagonian town of San Carlos de Bariloche in Argentina, which he visited this week. The Nazi hunter believes Heim is hiding out somewhere between the two towns, separated by the Andes mountain range.

“There is increasing pressure on Heim and on his family,” Zuroff said Thursday. “People under pressure make mistakes,” he added.