The world's top Nazi-hunter said Thursday that he had 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, told a news conference 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. "We're better off than before we came," Zuroff said. "That doesn't guarantee Heim's capture, but I'm hopeful." 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 she 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. Zuroff told The Associated Press that the Puerto Montt trip was a "turning point" because he was able to speak face-to-face for the first time with acquaintances of Heim's daughter and raise awareness among locals. "These are people who brought us specific details that gives us something concrete to latch onto," said Sergio Widder, the center's Latin American representative. He declined to elaborate. Heim was indicted in Germany after World War II on charges he murdered hundreds of inmates at the Mauthausen concentration camp in 1941. The Wiesenthal center says he injected the corrosive poison phenol directly into the hearts of many and used "other torturous killing methods." Zuroff says Heim's children have made no claim to a bank account with â‚¬1.2 million ($1.6 million) and other investments in Heim's name. To do that, they would have to produce proof that "Doctor Death" is dead. He said he's been tracking recent requests by Heim's lawyers for legal documents related to his estate that "would have no value if he is dead." He would not give details. A reward of â‚¬315,000 ($495,000) is being offered jointly by the center, the German and Austrian governments and a private donor for information leading to his capture. Heim tops the Wiesenthal Center's list of most-wanted Nazi war criminals. Zuroff met Thursday morning with Argentine Justice Minister Anibal Fernandez, who said the government will facilitate Heim's arrest and extradition if Heim is found in the country. Although World War II ended more than 60 years ago, the center continues to take on new cases as Nazi sightings surface. Between March 2007 and 2008, the Wiesenthal Center opened 202 new investigations, Zuroff said. The South American probe is part of the Jewish human rights organization's "Operation: Last Chance" - an effort to bring aging war criminals to justice before they die. If alive, Heim would be 94. Answering critics who say Heim's age undermines the validity of the hunt, Zuroff said to "keep in mind what he did when was a very young person." "If we put a limit on age, in a practical sense that means we're saying you can get away with genocide, which is morally outrageous," he added. After World War II, Heim was held for two and a half years by the United States military but was released without being tried. He disappeared in 1962 after he was tipped off that German authorities were about to indict him, Zuroff said.