An Austrian filmmaker believes he has discovered a huge Nazi “secret weapons facility” in an underground complex near the remains of the Mathausen-Gusen concentration camp in Austria, where thousands of Jews were killed.

“This was a giant industrial complex and most likely the biggest secret weapons production facility of the Third Reich,” documentary filmmaker Andreas Sulzer told the Sunday Times. The underground complex is connected to the B8 Bergkristall underground factory, where Germans produced the first jet fighters, the Messerschmitt Me 262.

Though the full scope of what occurred inside those reported chambers in the Austrian town of St. Georgen remains unclear and Sulzer’s conclusions are speculative, some analysts are already trumpeting the findings. The “filmmaker opened an important door that one has to go through,” Samuel Laster, editor of a Vienna newspaper, told the Jeursalem Post.

It was that facility where Nazi leadership possibly “aspired to create a combination of missiles and weapons of mass destruction,” historian Rainer Karlsch, who has long researched Hitler’s pursuit of an atomic bomb and worked with Sulzer on the project, told the Sunday Times. “They wanted to equip [a V-2] missile, or more advanced rockets, with poison gas, radioactive material or nuclear warheads.”

The reported findings, if corroborated by further inquiry, could add fresh fodder to an ongoing debate over the Third Reich’s ultimately failed attempt to secure an atomic weapon. The project, begun in the late 1930s, was called the “Uranium Society” or the “Uranium Club” by German scientists. It was inspired by a report by a pair of German chemists named Fritz Strassmann and Otto Hahn who detailed the mechanisms of nuclear fission.

Sulzer’s quest to discover what he called the Third Reich’s “biggest secret weapons facility” began years ago with the discovery of an off-hand remark buried in a letter written by a German scientist named Viktor Schauberger. Schauberger, Sulzer told the Sunday Times, “was involved, under the strictest secrecy, in research projects for the SS in St. Georgen. … In his letters he talks about splitting the atom,” Sulzer said. He added in an interview with the Sunday Times: “He warned colleagues in letters that he was involved in ‘atom-smashing.”

Sulzer then uncovered additional evidence suggesting the Nazis had perhaps conducted highly secretive weapon experiments in the same location, maybe even atomic experiments. In February of this year, after tests revealed unusually high radiation levels, drilling started near a vast network of tunnels constructed by concentration camp prisoners. The search for secret laboratories sought to answer a question that consumed the community: Did Hitler try to build an atomic bomb there?

“We just want to know whether a potential hazard exists,” the mayor of Perg in northern Austria told the Sunday Times. “We want hard facts.”

Then last week, the news broke in the German press. After heavy equipment cut through large granite plates Nazi troops used to seal an entrance shaft at the site, the team, using radar, found catacombs that coursed through an underground facility of roughly 75 acres.

It was already known that, as World War II raged, thousands of prisoners in the camp were used to construct massive underground facilities in St. Georgen that would be safe from the Allied bombing campaigns. In those facilities, workers produced rockets and fighter jets.

But perhaps other production was also quietly occurring. The head of the SS, Heinrich Himmler, who had lots of biological weapon schemes, was a regular visitor to the St. Georgen. It was also frequented, according to the filmmaker, by the man who directed Hitler’s missile programs, Hans Kammler. What’s more, Sulzerunearthed blueprints that he said showed additional, undiscovered chambers underground.

Then the biggest clue emerged. He found testimony by a top American operative who kept tabs on Nazi scientists who said there was a major complex hidden underground near St. Georgen. “We found these very, very interesting documents that point out that there was a very secret project going on in St. Georgen,” Sulzer told Russia Today earlier this year. “It could also be associated with atomic research.”

But there was a problem: Austrian authorities had pumped the tunnels full of concrete at a cost of millions of euros. And now, just as Sulzer’s team, which is funded by German state television network ZDF, may be close to discovering what happened there, local Austrian authorities stopped further excavation, requesting additional permits. Sulzer, however, told the Sunday Times he thinks they’ll start up work again in the coming weeks.

“Prisoners from concentration camps across Europe were handpicked for their special skills — physicists, chemists or other experts — to work on this monstrous project,” the filmmaker said. “And we owe it to the victims to finally open the site and reveal the truth.”