to a meteoritic origin. Since the crater field's discovery, hundreds iron pieces have been recovered, weighing from a few milligrams to 34 tonnes. Otumpa, a mass of approximately 1 tonne, was discovered in 1803. A portion of this mass was taken to Buenos Aires in 1813, then donated to the British Museum. Other large fragments are summarized in the table below. The mass called El Taco was originally , but the largest remaining fragment weighs . In 1969 El Chaco (the second-largest mass at ) was discovered below the surface using a metal detector. It was extracted in 1980 and, at the time, was estimated to weigh about 37 tonnes. This made it the second heaviest meteorite after the 60-tonne Hoba meteorite, discovered in Namibia. Currently, more than 100 tonnes of Campo del Cielo fragments have been discovered, making it the heaviest set of such finds on Earth. In 1990 an Argentine highway police officer foiled a plot by Robert Haag to steal El Chaco. It was returned to Campo del Cielo and is now protected by provincial law. In 2015, police arrested four alleged smugglers trying to steal more than of protected meteorites. In 2016, the largest-known meteorite of the strewn field was unearthed. Named the Gancedo meteorite after the nearby town of Gancedo, which lent equipment to aid in the extraction, this nickel-iron meteorite has a mass of (less than the original estimated mass of El Chaco). Due to a suspected lack of precision when El Chaco was weighed in 1980, the latter was reweighed with the same instruments and discovered to only have a mass of , making Gancedo the largest Campo del Cielo fragment recovered. The meteorite impact, age and composition At least 26 craters make up the Campo del Cielo crater field, the largest being . The field covered an area of with an associated strewn area of smaller meteorites including an additional . At least two of the craters contained thousands of small iron pieces. Such an unusual distribution suggests that a large body entered the Earth's atmosphere and broke into pieces, which fell to the ground. The size of the main body is estimated to have been larger than in diameter. Samples of charred wood were taken from beneath the meteorite fragments and analyzed for carbon-14 composition. The results indicate the date of the fall to be around 4,200–4,700 years ago, or 2,200–2,700