The now-shuttered the Bannister Federal Complex was built during World War II to make engines for Navy fighter planes, but it transitioned to producing parts for nuclear weapons in 1949.

The Department of Labor lists 2,498 toxic substances used at the plant over the years. The latest investigation by the National Institute for Occupational Safety and Health and an advisory board appointed by the president has turned up proof that operations at the site in the 1950s, ’60s and ’70s involved more radioactive materials than previously disclosed, The Kansas City Star (http://bit.ly/1P0uTNC) reported.

Multiple federal agencies and the plant’s contractors repeatedly claimed there were no significant health risks for workers at the complex. But the government now acknowledges that work with natural uranium — which emits about twice as much radioactivity per gram as depleted uranium — took place at the plant in the early 1950s. Workers also were exposed to magnesium alloys containing the radioactive element thorium in the 1960s and ’70s, in addition to other radioactive materials.

Workers who might have unknowingly been exposed include janitors, clerical workers and waste handlers whose radiation levels were not closely monitored.

More than 1,440 workers who became sick applied for compensation and medical coverage from the federal government, and nearly 300 of them received more than $55 million in compensation for illnesses linked to their work, according to an analysis of government data obtained by McClatchy Newspapers. In more than half of the cases, the money went to the workers’ surviving family.

But most who applied got nothing, including the families of at least 554 workers who died.

The 23 percent approval rate for former workers’ cases is less than half the national average.

Because of the new data, government officials will change the dose reconstruction formula used to evaluate claims. Some workers’ dose calculations might increase, though it’s unclear whether that will affect the decisions for any claims.

The Bannister complex is slated for demolition and redevelopment in the coming years.

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Information from: The Kansas City Star, http://www.kcstar.com.