DURHAM, N.C. (AP) — A former Duke University student believes she has solved the mystery of how the eight Confederate crew members on board the world's first submarine to sink an enemy warship were killed, but the researchers with access to the sub say her theory is not new.

Rather than having drowned or suffocated, the men were actually killed by the same weapon they wielded, according to Rachel Lance, who earned a Ph.D. in biomedical engineering with her research last year.

The explosion from a keg of gunpowder from a 16-foot (5-meter) pole that stretched out from the H.L. Hunley in February...