A deadly cancer riddling Australia's Tasmanian Devil has been found in an area thought to be free of the disease, troubling officials struggling to keep the animal alive in the wild. The facial tumour disease has so far been confirmed across more than 60 percent of the small island state of Tasmania, but it came as a surprise that it was found in one animal in the Zeehan area in the state's west. "Although our monitoring does indicate a westward movement of the disease, and we expected to continue to detect cases west of the known perimeter, this detection is not in an area we expected to see the disease at this stage," Save the Tasmanian Devil Program's Howel Williams said Friday. The furry marsupials were declared endangered in 2009 after the contagious cancer began sweeping through the population, disfiguring their faces so badly they are unable to eat and starve to death. Estimates suggest that some 70 percent of devils have already been lost to the infectious disease, which is spread by biting. Williams said the sickness, which scientists believe could see the entire wild population of devils vanish within 20 to 50 years, was unusual in its persistence. The detection of a case beyond the known perimeter highlighted to officials that they could not rely on a single measure to conserve the species in the wild, he said. Williams said the government had a "thriving" insurance population of Devils, which secured the animals's long-term future in captivity and was working to keep other areas in the wild free of the disease. Williams told ABC Radio that officials would press ahead with plans to build a 12.5 kilometre (almost 8 mile) fence to protect healthy devils in the wild from infected animals in one part of the state's west. Tasmanian devils first came to prominence when their unearthly shrieks and grunts while devouring corpses of dead animals terrified European settlers arriving on the island in the 19th century.