Officials in Chile say they\'re investigating the poisoning of at least 20 Andean condors that resulted in the death of two of the giant endangered birds. The huge birds, with a wingspan of up to 10 feet, were found near the town of Los Andes, about 50 miles of Santiago, after witnesses told authorities of seeing the birds flying low and crashing into rocks, the BBC reported Tuesday. Once on the ground, they were unable to take off again and walked in an apparently dizzily manner, authorities said. In addition to the two birds that died, two dead foxes were found. Official says they believed the birds might have been affected by eating carcasses of poisoned cattle, fox or puma. \"[The poisoning] seems to have been caused by the ingestion of an ill animal or one that ate another being with some phosphorate compound,\" Pablo Vergera, the regional director of the Chilean Farming and Cattle Service, told a local newspaper. Phosphate compounds are found in herbicides and poisons used to kill animals considered to be pests. Eighteen of the poisoned condors were taken to a veterinary clinic where they were given an antidote and were said to be recovering.