Bomb disposal experts a say nine-hour operation to defuse a wartime shell in the Tseung Kwan O landfill on Friday was especially difficult because it was ready to explode and had an extremely thick casing.
Officers say the World War Two device weighed about 150kg and contained 50kg of high explosives.
Superintendent Suryanto Chin-chiu said their operation was difficult and presented different challenges to the bomb found in Wan Chai in May.
"It was a bomb that was different from the last one that we discovered in Wan Chai. Last time it was an aircraft bomb, and this time it was a projectile.
We identified it was ... highly likely shot a by a naval gun from somewhere in Hong Kong but because the mud was dragged from somewhere else so it has to be further identified
"In comparison with the bomb that we found last time, the thickness is about 10 times. Because the bomb itself had been fired, all the safety measures had been removed. It was like one step away from detonation."
About 200 people in the area were evacuated before officers got to work.