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Hollywood legend John Wayne died 40 years ago, succumbing to cancer aged 72. In 1954 he worked on a film called 'The Conqueror,' which was filmed on location near the US government's atomic testing range. By 1980 according to People magazine, 91 of the cast and crew had contracted cancer. Of these, 46 had died of the disease, including Wayne himself. A sad coincidence? Or did radioactive fallout succeed in nearly killing 100 people involved in the production of a Hollywood movie?

Browse the gallery and learn more about this disturbing and still controversial story.

▲'The Conqueror' starred John Wayne as Mongol chief Temujin (later known as Genghis Khan). It is considered one of the worst casting decisions in cinema history! His costars were Susan Hayward, Agnes Moorehead, and Pedro Armendáriz.

▲Temujin falls for Börte, a beautiful princess and daughter of a rival Tartar warlord. He lures her away, but is spurned. He snatches her back in a raid, but is later captured.

▲Eventually Börte falls in love with the dashing Mongol chief and helps him escape. But Temujin is convinced he was betrayed by a fellow Mongol and vows to unmask the traitor and overthrow the Tartars.

▲Wayne as Khan notwithstanding, 'The Conqueror' is often ranked as one of the worst films ever made. And there the story should have ended, a Hollywood flop languishing forever in cinema's vault of shame. Except it didn't!

▲The film was shot from June through August 1954 among the copper-hued canyons and ivory dunes near St George, Utah—a location chosen by director Richard Powell for its scenic resemblance to the central Asian steppes.

▲However why no one discovered the fact that St George lies 220 km (137 miles) downwind of the US government's atomic testing range at Yucca Flat, Nevada (pictured) remains one of the great mysteries of this story. What is certain though is that 'The Conqueror' film set was constructed over a radioactive environment.

▲Filming continued, with cast and crew seemingly oblivious to the danger. However, Wayne at least appears to have been aware of the presence of radiation. A photograph illustrating a Guardian newspaper report shows the actor clutching a Geiger counter and checking a patch of scrub, with sons Michael and Patrick looking anxiously on.

▲The NNSS was established in January 1951 for the testing of nuclear devices. Above-ground nuclear explosions at the range went on until August 1963. Operation Ranger (pictured) was the first series of tests to be carried out.

▲The Atomic Energy Commission (AEC) posted notices warning the public of impending test activities. "Health and safety authorities have determined that no danger from or as a result of AEC test activities may be expected outside the limits of the Las Vegas Bombing and Gunnery Range..."

▲In late 1951, Operation Buster–Jangle took place. These tests involved the mobilization of 6,500 ground troops in what became known as Operation Desert Rock.

▲No bombs were tested during the actual filming of 'The Conqueror.' But 11 were detonated the year before.

▲One of these was the infamous Grable shot, a 280mm shell fired from the "Atomic Cannon"—the first time an atomic artillery shell had been fired.

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The innocuous-sounding Operation Teapot was a series of fourteen nuclear test explosions conducted at NNSS in 1955. Filming of 'The Conqueror' had wrapped the previous summer and was in post-production.

▲Powell chose Snow Canyon to film battle scenes. A wind-trap, it's believed the canyon floor had collected radioactive dust from previous blasts, which was subsequently whipped up by hundreds of extras, as Mongols fought Tartars under a hot desert sun. Was this deadly dirt a contributory factor in what was about to be played out?

▲After exterior scenes had been shot, the film's producer Howard Hughes later shipped 60 tons of sand back to Hollywood in order to match the Utah terrain and lend realism to studio re-shoots. Whether plagued by guilt or some other reason, the billionaire would later buy up all the copies of 'The Conqueror' and reputedly watched the film every night in his final, reclusive years.

▲'The Conqueror' was released in 1956. Despite a modest box-office return, the film was a critical failure, and became a laughing stock.

▲Within a few years the film had garnered a more sinister reputation. Several of the cast and crew fell ill. Powell was diagnosed with lymph cancer and died in January 1963.

▲Powell's daughter Ellen (seen here on set with her father) believed his early demise was as a direct result of the radioactive environment he'd worked in, and pointed the finger at the authorities, asking angrily: "How dare people not be warned if there is some knowledge of even a potential danger?"

▲Five months after Powell's death, Mexican actor Pedro Armendáriz, who'd played Jamuga in the film, also died, having committed suicide after being diagnosed with terminal neck cancer. Armendáriz, however, never believed that the atomic tests might have been responsible for his condition.

▲In 1964 John Wayne was diagnosed with lung cancer and had his left lung removed. Although he declared that he'd "licked the Big C," the actor's years were by then already numbered. Wayne also denied radioactive fallout could be responsible for his ill health, instead declaring that a heavy smoking habit was the likely culprit.

▲In contrast to her stricken costars, Agnes Moorehead was sure "radiocative germs" were responsible for the uterine cancer that eventually killed her in 1974. "Everybody in that picture has gotten cancer and died," she lamented. "I should never have taken that part."

▲Hayward had portrayed Börte in the film and like Wayne, was a heavy smoker. But her family believed her death in 1975 from brain cancer may well have been as a result of radioactive fallout from atmospheric atomic bomb tests. Her son Tim Barker later echoed Ellen Powell's words when he said bitterly: "If the government knew that there was a possibility of exposure, why didn’t they just warn us?"

▲John Wayne's sons, Patrick and Michael, experienced cancer scares in the mid-1970s. Both had visited their father on the set of 'The Conqueror.' Patrick (pictured) was operated on for a benign tumor. He is today chairman of the John Wayne Cancer Institute.

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Michael Wayne developed skin cancer in 1975, but it was heart failure that eventually claimed the life of the eldest son of the Hollywood legend.

▲John Wayne's cancer returned with a vengeance, and the film star died in 1979. The following year People magazine carried a quote from a scientist from the Pentagon’s defense nuclear agency: "Please, God, don’t let us have killed John Wayne."

▲According to the People magazine article, of the film's 220 cast and crew members from Hollywood, an astonishing 91 had by 1980 contracted cancer. Of these, 46 had died.

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Today residents living in and around St George (pictured) still live with the legacy of those atomic tests of 60 years ago. The Radiation Exposure Screening and Education Program reported that of all the patients admitted to just one St George medical center in 2015, 60% were new cancer cases, mostly breast, thyroid, leukemia, colon, and lung cancers.

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As a film, 'The Conqueror' is long forgotten. But for anyone who's been affected by the fallout from those terrifying nuclear explosions, they'll never forget.