Hong Kong: Authorities in Hong Kong will evacuate around 6,000 residents after a World War II-era bomb was discovered at a construction site in the city’s Quarry Bay area, police said Friday.

The bomb, measuring about 1.5 metres (4.9 feet) long and weighing roughly 450 kilograms (1,000 pounds), was found during excavation. Police believe the device remains “fully functional,” posing a serious risk if mishandled.

“Due to the extremely high risks involved in dismantling and disposing of the bomb, we must activate the emergency evacuation plan,” district commander Andy Chan told reporters.

Residents from 18 buildings in Quarry Bay will be evacuated on Friday night, with disposal work scheduled to begin early Saturday. Police estimate the operation will take about 12 hours. They noted the bomb contained 500 pounds of explosives, warning it could have caused “massive casualties” if detonated accidentally.

Hong Kong was among the first targets of Japan’s military campaign in Asia during World War II and witnessed intense battles between Japanese and Allied forces. Nearly eight decades later, unexploded ordnance is still occasionally unearthed by hikers and construction crews.

In May 2018, a similar bomb was discovered in the city’s Wan Chai district, forcing 1,200 residents to evacuate. Police said the device found on Friday is the same type as the one from 2018, which took nearly 20 hours to defuse.