The experts from Krakow's prestigious Academy of Mining said a tunnel could exist but that there was no sign of a train at a site near the southwestern town of Walbrzych.
The story sparked a flurry of global media interest in September when two men claimed to have discovered an armoured Nazi train using ground-penetrating radar.
Piotr Koper, a Pole, and German national Andreas Richter said a train carriage 98 metres (320 feet) lay buried eight to nine metres underground.
They said they believed the contents were mostly weapon prototypes, though local legend spoke of artwork, jewels and gold stolen by the Nazis.
The Nazis made prisoners of war dig a network of tunnels in the area, and some locals have claimed the Germans tried to spirit gold away as Russia's Red Army closed in.
But Academy geology professor Janusz Madej said his team's research had indicated "there is no train on this site (but) "maybe a tunnel".
While admitting that a geological survey of the area had thrown up some anomalies, Madej told AFP he was "100 percent sure there is no train" there based on magnetic, gravimetric and geo-radar studies.
Koper and Richter insist that further searches will locate a train buried deep inside the tunnel.
"We discovered a tunnel. You can see clearly the entrance to a tunnel," Koper told reporters.
He told AFP his team would prove that a train exists.
"I am convinced we are going to prove its existence. We need a bit more time ... we need to excavate," he insisted, adding that he and Richter were prepared to foot the bill themselves.
It will ultimately fall to the Walbrzych town hall to decide whether excavation should proceed.
Treasures that the Nazis allegedly stashed away as Soviet forces closed in reputedly included artwork stolen from dispossessed Jewish families and the Amber Room, which the Germans pillaged from Saint Petersburg's Catherine Palace.
Quite apart from the train legend, it was at Walbrzych that the Nazis constructed a huge subterranean labyrinth over 200 hectares (500 acres) beneath the hills of Lower Silesia -- including around the massive Ksiaz Castle.
The huge bunker, which cost the lives of countless concentration camp inmates who hewed out the rock, was supposed to provide shelter from attack for Hitler's general staff -- as well as store treasures looted from across Europe.
The entrances were dynamited to erase all trace of the proposed hideout.