HONG KONG — One spud was a dud.

Caked in rust and mud, a World War I hand grenade was harvested with potatoes in France and shipped to a potato chip factory in Hong Kong — until a machine found that one was not quite like the others.

The bomb, a German-made device that was in an unstable condition, was defused by the Hong Kong police at the factory on Saturday using a “high-pressure water firing technique.”

“Since the grenade had not blown up at the time it was thrown, there was an immediate danger that needed to be handled right away,” Superintendent Wong Ho-hon said.

At 2.2 pounds, with a 3-inch diameter, the grenade was about the size of a potato, but was around five times as heavy.