Army experts use mine detectors to check for explosives in an area where, according to two explorers, a secret tunnel is hiding a World War II Nazi train with armaments and precious minerals. (Associated Press)

Seventy years ago, it is rumored, an armored train departed for the Polish city of Walbrzych in the waning days of World War II. It snaked stealthily through the thickly forested mountains of southwestern Poland, carrying an untold fortune in Nazi loot: gold, jewels, art, maybe even weapons confiscated from Polish citizens and sent into the interior for safekeeping as the German regime began to crumble.

But the train never arrived.

Instead, it’s thought to be sealed inside one of the tunnels built by slave laborers for the Nazis, who were occupying a castle just above the underground network. And there it remained, the subject of rampant speculation and several investigations that brought locals no closer to the train and its riches — if they even existed in the first place.

The latest report of discovery came in August of this year, when two treasure hunters said they’d determined the location of the train by using a map drawn by a man on his deathbed. But their claim doesn’t seem to have panned out. On Tuesday, experts from Krakow’s AGH University of Science and Technology said that a month of magnetic and gravitational surveys has revealed no trace of an underground rail system or the treasure train that supposedly rode along it.

Project leader Janusz Madej said the scientists found some anomalies, but they were just eight feet below the surface — not deep enough to be anything matching descriptions of the train’s hiding spot.

“There may be a tunnel,” Madej said at a news conference, “but there is no train.”

[A frenzy in Poland over the latest mysterious ‘Nazi gold train’]

Piotr Koper and Andreas Richter, the amateur explorers who claimed to have located the train four months ago, were less convinced by the scientists’ findings. At the same news conference, they said their own research team had found further proof of the train’s existence: images from ground penetrating sensors that showed clear signs of a tunnel laid with tracks and sleepers and several shapes below ground that could only be the fabled vehicle.

“We carried out similar examinations in many other locations, but we have never encountered anything like this,” Koper said, according to the New York Times. “There is no way these shapes are of natural origin.”

The pair said they were only hobbyists — Koper is a Polish construction company owner, Richter a German geologist — but said they stood by their claims.

“There can’t be a mistake,” Koper said.

“It’s human to make a mistake,” Madej responded. “But it’s foolish to stand by it.”

Ksiaz castle in Poland. During World War II, Adolf Hitler began to build a system of long tunnels underneath the castle. (AP)

If the Nazis really did have a secret treasure train in Poland (as they were known to have elsewhere), the area around Walbrzych is where they would hide it. The sleepy city is surrounded by dense forest and the Owl Mountains and is home to the 800-year-old Ksiaz castle, built by a man known as “the Raw” and occupied by Adolf Hitler himself.

Eduard Wawrzyczko, who had worked as caretaker at Ksiaz for nearly half a century by the time the German soldiers arrived at the castle, recalled the occupation to the New York Times in 1961.

“In 1943, Hitler came here with [Nazi official Hermann] Goering and they went through the castle,” he said. “Then the pillagers came and they turned Ksiaz into this.”

“This” was an austere ruin, gutted of its baroque finery and converted into barracks. Any valuables that had been left in the castle when the noble family who lived there fled in 1938 was seized by the Nazis and carted away. Elaborate ceiling frescoes were obscured with a layer of whitewash and mosaics torn out of the tile floors.

Then came the slave laborers, Jews and political prisoners taken from concentration camps to work for the infamous Todt Organization, the Nazi’s quasi-military construction wing.

They were there to build a network of tunnels, Wawrzyczko said, for a scheme dubbed “Project Riese” or “giant.” The tunnels were never completed, and their purpose remains unknown. Many believed that Hitler intended to move into Ksiaz castle and make the underground fortress his new headquarters. Others thought that the subterranean caverns were to be a storage space for weapons — perhaps, some conspiracy theorists say, “Die Glocke,” the purported Nazi superweapon so far only found in the pages of science fiction novels. Then there’s the notion of the secret rail system, where the treasure train may have been stored.

The area was abandoned when the Red Army took control of southwestern Poland in 1945, with only five miles of tunnels dug and much of it structurally unsound. But as the Nazis fled, some German miners claimed to have seen a train being wheeled into a tunnel beneath the mountains, according to Smithsonian Magazine. They told a Polish miner, who told others, and a rumor was born.

Part of a subterranean system built by Nazi Germany in what is today Gluszyca-Osowka, Poland. (AP)

Reports that something had been found in the Nazi complex’s ruins flared up periodically, including in 1961, when the Times sent a reporter to interview Wawrzyczko. It had been reported that Polish army units were excavating the crumbling tunnels — perhaps in search of treasure. But nothing was ever found.

Decades later, despite numerous false starts and failed searches, the rumor persists. Though few people in Walbrzych remember the Nazi presence during the war, they all know the story of the tunnels and the treasures they supposedly contain. In the months since Koper and Richter staked their claim (along with legal documents requesting 10 percent of the treasure, if it’s found), that speculation has been fanned into an all-out frenzy. Journalists have descended on the city, along with amateur treasure hunters toting metal detectors, according to the Guardian. The Discovery Channel signed an agreement for exclusive rights to film the scientists’ survey — a deal that must seem slightly sour now that the researchers turned up nothing.

The disagreement between the treasure hunters and the researchers about evidence of the train leaves city officials in something of a quandary, according to the New York Times. They can move forward with expensive plans to lower cameras into the supposed tunnel through holes in the ground. Or they can chalk it up as yet another unproven rumor and move on. Wait for another claim to arise, as they inevitably do.

Wawrzyczko thought that treasure hunters would be waiting a long time.

The Nazis “took away the pictures and everything long before the tunnels were dug,” he said in 1961. “There is nothing left here.”