Machu Picchu grown rapidly. In 1912, 1914 and 1915, Bingham removed thousands of artifacts from Machu Picchu—ceramic vessels, silver statues, jewelry and human bones—and took them to Yale University for further study, supposedly for 18 months. Yale instead kept the artifacts until 2012, arguing that Peru lacked the infrastructure and systems to care for them. Eliane Karp, an anthropologist and wife of former Peruvian President Alejandro Toledo, accused Yale of profiting from Peru's cultural heritage. Many of the articles were exhibited at Yale's Peabody Museum. In 2006, Yale returned some pieces but kept the rest, claiming this was supported by federal case
Machu Picchu zone exists above the area. UNESCO is considering putting Machu Picchu on its List of World Heritage in Danger. During the 1980s a large rock from Machu Picchu's central plaza was moved to a different location to create a helicopter landing zone. In the 1990s, the government prohibited helicopter landings. In 2006, a Cusco-based company, Helicusco, sought approval for tourist flights over Machu Picchu. The resulting license was soon rescinded. Authorities have struggled to maintain tourist safety. Tourist deaths have been linked to altitude sickness, floods and hiking accidents. UNESCO received criticism for allowing tourists at the location given high