Rumor has it, a Nazi train loaded with looted gems and treasure vanished en-route to Berlin in southwestern Poland at the end of the Second World War, though many experts dispute its existence. In the midst of international speculation and intrigue, two explorers are literally digging their way to the truth.

Piotr Koper of Poland and Andreas Richter of Germany believe the mysterious train was hidden from the Soviet Red Army in a secret tunnel constructed by Nazis near the Polish city of Walbrzych. Soil anomalies detected in the area with radar equipment last year indicate its presence, they claim.

Geological experts from Krakows AGH University of Science and Technology found no evidence of the train when searching with magnetic equipment, the Associated Press reports, but their findings did conclude that there may in fact be a tunnel located at the site of Koper and Richters privately-funded excavation.