Warsaw - Explorers in Poland began digging on Tuesday for a legendary Nazi train said to be laden with treasure and armaments.They're not dissuaded by decades of fruitless searches, a scientific determination that no train is there and warnings by historians that such a train might not even exist.The search in south-western Poland attests to the power of a local legend claiming a Nazi "gold train" disappeared in a mountain tunnel as the Germans escaped the advancing Soviet army at the end of World War II.As the dig got underway, a yellow excavator moved earth along railroad tracks above the spot where two explorers - Andreas Richter, a German, and Piotr Koper, a Pole - believe the train is buried. Richter and Koper, joined by several other volunteers, expect the search to last several days.The two men claimed last year to have located the elusive train with radar equipment deep in the bowels of the earth in the city of Walbrzych, sparking a gold rush to the castle city and the surrounding area.A government official initially said he was "99% sure" the train was there, helping to feed the frenzy. The arrival of treasure hunters and curiosity seekers from across Europe gave a welcome financial boost to the coal mining region of Silesia, which has struggled since unprofitable mines in the area were closed after the fall of communism.No giving upLate last year, geological experts from a university in Krakow, using magnetic equipment, found no train on the spot.But the explorers refused to give up.Andrzej Gaik, a spokesman for the search team, said six independent companies using various radar devices have detected anomalies indicating the shape of a tunnel underground on an elevated area running along railroad tracks."The results of the ground-penetrating radar examinations are very promising," Gaik said. "It's so exciting and we count on success."Historians say the existence of the train, which is said to have gone missing in May 1945, never has been conclusively proven. Polish authorities nonetheless have seemed eager to pursue any chance of recovering treasures that have sparked the imaginations of local people for decades.At the height of the frenzy last year, the World Jewish Congress reminded Poland's authorities that, in the case of a discovery of a treasure-laden train, any valuables belonging to Jews killed in the Holocaust must be returned to their rightful owners or their heirs.Legend holds the train was armed and loaded with treasure and disappeared after entering a complex of tunnels under the Owl Mountains, a secret project known as "Riese" - or Giant - which the Nazis never finished.The area belonged to Germany at the time, but has been part of Poland since the borders were moved in the post-war settlement.Living source of the legendA man credited with being the main living source of the legend is a retired miner, Tadeusz Slowikowski. He heard from a German man in the 1970s of a train that left the German city of Breslau (today Poland's Wroclaw) in the spring of 1945, as the Soviet army approached. He said the man told him the train disappeared before ever making it to Waldenburg (now Walbrzych) about 65 kilometres to the west.However, a local historian, Pawel Rodziewicz, told The Associated Press last year that documentation leaves no doubt that gold in Breslau was evacuated to the German central bank in Berlin and elsewhere, so there would have been no reason to take any to Waldenburg, where the approaching Soviets could find it.He thinks it is impossible that a secret railway tunnel could have been built into the hill near railroad tracks in frequent use. No documents have ever been found to indicate such a project was undertaken, while documents exist even for the most top-secret projects of the Third Reich, including some for the subterranean tunnels beneath the Ksiaz Castle in Walbrzych, Rodziewicz argued.