They found one while digging the foundations of a new hotel.
Another was discovered in the middle of a park.
A family spotted one in their garden.
And Ho Van Lai and his cousins found several in the sand dunes, strange, rusted objects, no larger than a tennis ball.
"I was just a 10-year-old boy, I was reckless," Lai said through a translator.
Lai was playing with something that can be found across Vietnam: cluster munitions.
And not understanding the risk, he picked up a rock and knocked it against those munitions.
"The explosion killed my two cousins immediately," he said.
"I lost my right hand, my right arm and part of my left hand. I lost my two legs and one of my eyes."
The war is over, the danger is not
Lai lived near a former US military base in central Vietnam, not far from the "demilitarised zone" that once separated the communist North from the capitalist South.
The explosives were the remnants of a two-decade struggle between these two powers and their ideological allies, including China and the Soviet Union in the north and the United States and Australia in the south.
The war involved one of the largest aerial bombing campaigns in history, with the US dropping double the tonnage of explosives on Vietnam than were dropped by all of the allies during World War II.
And while these bombs killed countless soldiers and civilians, some never detonated.
They were swallowed by the jungle, buried underground or covered by reconstruction.
And since 1975, these explosives have caused an estimated 100,000 causalities, including 40,000 deaths, according to the Vietnam National Mine Action Center.
"The Vietnamese people should have peaceful and safe lives," Lai said.
"The war ended many years ago but bombs and mines left from that war still pose a lingering threat."
Area 'the size of Tasmania' still contaminated
This year marks the 50th anniversary of The Fall of Saigon, the moment when northern forces overran the capital, ended the war and reunited Vietnam.
But despite decades of investment by the Vietnam government, former adversaries like the United States and Australia, not-for-profits and communities, clearing the country of unexploded ordnance is proving almost impossible.
That's partly due to the sheer scale of the task, according to Sabina Stein from the United Nations Development Program.
"We're talking about a landmass roughly the size of the state of Tasmania that is still contaminated," she said.
"And a lot of this territory is not idle. A lot of development has taken place and at times this has led to incidents."
Vietnamese authorities estimate 18 per cent of the country is contaminated, a figure that has decreased by just 1 per cent in the past decade.
Risk-education programs, particularly those targeting children, farmers and those who sell scrap metal, have helped reduce the number of deaths and injuries.
But physical harm isn't the only harm that has endured long after the fighting stopped.
Investors wary of the risks
Vietnam is in the midst of rapid urbanisation, with major infrastructure projects across the nation.
But Ms Stein said projects were often delayed or made more expensive by the discovery of unexploded ordnance.
"While development has not stopped, it has slowed," she said.
"Many of the areas most affected are rural and more remote areas."
The added time, cost and liability of removing explosives can discourage investors, particularly in places like A Loui province, where large areas are contaminated by landmines and ordnance.
"This is a place that has huge tourist potential, it's beautiful," Ms Stein said.
"And definitely that potential has been highly constrained by an inability to develop major infrastructure projects."
But some locals don't have the luxury of avoiding contaminated regions.
"Farmers continue often to use land even though they know it's dangerous, but this is a result of land scarcity," Ms Stein said.
"It has meant that a lot of farming avoids mechanised farming methods, which can be more high risk.
"Which is problematic in a country that has ambitious development goals and wants to continue in what has been really an admirable path of poverty reduction."
Removing bombs is back-breaking work
The labour-intensive nature of explosive clearance often requires strong coordination between governments, not-for-profits and local communities.
Sarah Goring leads the Vietnam wing of the Mine Advisory Group (MAG), which has worked to remove landmines, cluster munitions and unexploded bombs in more than 70 countries since 1989.
"We're trying to clear the priority areas. So where people are working, where people are living," she said.
"Maybe they're building a new kindergarten and we go and clear it before they build."
Alongside risk education, MAG do the painstaking work of clearing land in the highly contaminated provinces such as Quang Tri and Quang Bing.
When explosives are uncovered, some are sent to regional depots for disposal.
Others are so volatile they are detonated on site.
Ms Goring remembers one instance where a 330-kilogram bomb was found during a home renovation.
"This is real life for people. They find bombs all the time," he said.
"Despite the legacy of the war and that it continues to impact people today, they are so positive and so about moving forward and making the best of a situation."
Explosive legacy casts a long shadow
Those dedicated to the cause know it may be impossible to locate absolutely every explosive hiding above or below the surface.
But new techniques, including satellite imagery, mobile phone reporting and social media education campaigns are helping reduce the threat.
Today, Lai shares his story with students as part of a risk-education program at the Mine Action Visitor Centre, which is run by humanitarian organisation Project RENEW.
"I've been doing quite meaningful work to prevent harmful accidents," he said.
"I feel I am living as a helpful person to the society now."
One day, the risk of unexploded ordnance may be so low that this work will no longer be necessary.
But Ms Stein warns that many other countries will have to tackle the same challenges as Vietnam.
"It's going to be the reality for an increasing number of countries that have experienced such intensive bomb campaigns. We can think of countries like Iraq, Syria, occupied Palestinian territories, Ukraine," she said.
"As we near the 50th anniversary of the end of the war, it is a very strong reminder of the multi-generational effects of such devastating aerial bombing campaigns."
