Evidence of Neolithic habitation of areas in modern Karnataka and celts dating back to the 2nd century BCE were first discovered in 1872. There are reports that a polished stone axe was discovered at Lingsugur in the Raichur district; however the authenticity of these reports remains unverifiable. Megalithic structures and burial grounds were discovered in 1862 in the regions of Kodagu and Moorey Betta hills, while Neolithic sites were discovered in north Karnataka. Scholarly hypothesis postulates of contacts between the Indus Valley city of Harappa in 3000 BCE, citing the discovery of gold found in the Harappan sites that was imported from mines in Karnataka.