Story highlights Workers removed concrete plug before discovery

The cannon fired munitions aboard the British warship HMS Hussar

Authorities remove about 1.8 pounds of gunpowder and dispose of it at a gun range

Author: "It was there for so many years, and people were sitting on it"

This could have caused a major blast from the past.

Workers cleaning a cannon, last fired more than 200 years ago, were shocked to find Friday that it was still loaded with gunpowder, wadding and a cannonball.

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.

Dena Libner, a spokeswoman for the Central Park Conservancy, said the workers found the munitions after removing a concrete plug from the mouth of the cannon.

Workers immediately called 911, and technicians determined that the gunpowder was still active.

Authorities removed about 1.8 pounds of black gunpowder from the scene and took it to a gun range for disposal, the detective said.

Libner said the cannon was a gift from an anonymous donor to the city in 1865 and was stored for a period of time because of vandalism concerns.

It is now part of the organization's restoration program, she said.

"We silenced British cannon fire in 1776, and we don't want to hear it again in Central Park," New York police said in a statement to CNN affiliate WCBS

The loaded artillery piece was one of two Revolutionary War-era cannons being stored at the park's Ramble shed, near the 79th Street transverse, according to the affiliate.

"This was an amazing surprise," John Moore, author of the upcoming book "The Secrets of Central Park," told WCBS. "It was there for so many years, and people were sitting on it when it was a loaded cannon."

The Hussar sank in November 1780, according to the New York Journal of American History.