Police set up a cordon at a landfill off Wan Po Road in Tseung Kwan O on Friday, after a bomb was found on a worksite in the area.
The bomb squad conducted a detonation shortly before 6pm.
According to a witness cited by Apple Daily, more than ten police vehicles, five or six fire trucks and several ambulances were in attendance.
Nearly 100 people from the area were evacuated to a safe location, according to the witness.
The paper reported that workers found the explosive while digging up sand to be sent to a barge destined for the construction of the third runway at the Hong Kong International Airport.
A dump truck driver told HK01 that the police asked workers to drive dump trucks away from the area as they believed it was a genuine bomb, with one source saying that the bomb was from the Vietnam War.
A representative from the Hong Kong Dumper Truck Drivers Association told HK01 that the bomb was found in a public filling area managed by the CEDD. Fill banks are where materials such as construction debris, rubble, earth and concrete suitable for land reclamation are stored.
In May, hundreds were evacuated from Wan Chai after a World War II-era bomb was discovered at a construction site.