Thousands of mostly African-American soldiers were reportedly subjected to painful mustard-gas experiments during World War II because of their race.

The once-secret government program, which tested chemical agents on troops, was formally declassified in 1993.

A new NPR investigation found that it primarily targeted black GIs.

“They said we were being tested to see what effect these gases would have on black skins,” one said. Reports said the military was searching for soldiers who could be more resistant to the chemicals.