The bomb was found on May 30 at more than one meter underground three days earlier, when the family had workers dig up their backyard to make a pond.
It was only several meters from their house.
|A bomb found in the backyard of a house in Dong Thap Province May 27, 2016. Photo credit: Phuc Dien/Tuoi Tre
Officers said the bomb might have been there since the Vietnam War, which ended more than 40 years ago.
Unexploded ordnance still threatens a fifth of land mass across Vietnam and explosions occur frequently.
Deputy Minister of Defense Nguyen Chi Vinh said last October that the explosions kill more than 1,500 people every year and maim and injure 2,200 more.