An Austrian doctor accused of killing hundreds of inmates in a Nazi concentration camp during World War Two may be in Spain, the Nazi-hunting Simon Wiesenthal Center said on Saturday. Aribert Heim, 91, known as "Doctor Death", worked in the Mauthausen concentration camp in Austria and killed hundreds of inmates by lethal injection and torture, the center said. "As far as we know he is in Spain. There is speculation he might have left," Efraim Zuroff, the center's chief Nazi hunter, told Reuters in Jerusalem. He declined to elaborate further, but German weekly magazine Der Spiegel said investigators in Madrid had discovered that a relative of Heim's had transferred 300,000 euros over the past five years to a family friend living near Girona in northeastern Spain. The investigators suspect that some of this money may have been used to support Heim, it added, without giving any sources. The magazine also said there had been an increasing number of clues over the past few weeks that Heim may until recently have been living on Spain's Mediterranean coast near to Denia. Spanish police were not immediately available for comment. Zuroff said the Wiesenthal Center was working with German investigators and the authorities in Madrid to track down Heim. "My understanding is that he has not been caught yet, but it would not surprise me if he will be in the next few days," he said. The center says Heim worked as a doctor in Germany after the war but escaped in 1962 after he was about to be arrested. Germany and Austria both have outstanding arrest warrants for Heim, it added. Over the years Heim was believed to have been in Egypt and in South America.