The preservation workers from New York's Central Park Conservancy were removing rust from the antique cannon, which once fired munitions aboard the British warship H.

CNN: STORY HIGHLIGHTS

The preservation workers from New York's Central Park Conservancy were removing rust from the antique cannon, which once fired munitions aboard the British warship HMS Hussar, when they made the explosive discovery, New York police Detective Brian Sessa said.

CNN: STORY HIGHLIGHTS