Scientists led by an Indian-origin researcher have discovered a huge underground river which, they believe, is flowing some 13,000 feet beneath the mighty Amazon River in Brazil.

The researchers at Brazil's National Observatory (BNO) believe the subterranean river is about 6,000-km long, about the same length as the Amazon on the surface. The finding came from studying temperature variations at 241 inactive oil wells drilled in the 1970s by Brazil's state-run oil company Petrobras, the Daily Mail reported.

The researchers have named the river ‘Hamza', after team supervisor Valiya Hamza, an Indian-origin scientist who has been studying the region for over four decades.

It is believed the river originates from the region of Acre and reaches the sea at Foz do Amazonas, flowing through the basins of Solimoes, Amazona and Marajo.

The findings were presented recently at a meeting of the Brazilian Geophysical Society in Rio de Janeiro.