NORTH CHARLESTON, S.C. - Scientists say the submarine that was the first in history to sink an enemy warship was much closer than thought to a Union ship it sank in 1864.

Scientists announced Monday that 135 pounds of gunpowder was attached to a pole, or spar, at the front of the Confederate submarine H.L. Hunley.

It has been long thought the Hunley attached a torpedo to the bottom of the blockade ship Housatonic and then backed off. But new evidence indicates the Hunley was only about 20 feet away, meaning the concussion from the explosion could have knocked out the crew.

The Housatonic sank, while the Hunley, built in Mobile, Ala., never returned with its eight-man crew. The sub was found off South Carolina in 1995 and raised five years later.