Expedition to 'Lost Tribe' Lands Halted Museum fears operation could threaten Paraguay's Ayoreo By Rob Quinn, Newser Staff Posted Nov 16, 2010 5:01 AM CST 8 comments Comments The Gran Chaco is a vast area of dry forest that stretches into Argentina, Bolivia and Brazil. (Wikimedia/Ilosuna) (Newser) – A British expedition to a remote region of Paraguay has been halted to ensure that one of the world's last uncontacted tribes stays that way. The expedition from London's Natural History Museum had planned to search for new species of plants and insects in the Chaco wilderness, but officials feared that the 100-strong team might encounter members of the Ayoreo tribe and potentially pass on diseases that could wipe them out, the BBC reports. The Ayoreo are the only uncontacted tribe in Latin America outside the Amazon region. Some 150 tribe members are believed to be living a hunter-gatherer existence in the region. Hundreds of other have left the region in recent years as land was cleared for farming, and it is through these exiles that the tribe passed on its desire to be left in isolation. The museum says it is in negotiations with the Paraguayan government and indigenous leaders to find a way for the expedition to be able to record the region's biodiversity without risking the tribe's safety.