The company said it was disarming explosive materials prior to commencing the Lao Bao international border gate expansion project on October 5 when workers discovered 159 unexploded ordnances 2.5 metres below a basement.
The weaponry, including 33 missiles, bombs, grenades and shrapnel bombs, was later collected and brought to a storage facility.
The company is working closely with the border guard force at Lao Bao border gate to expand the search on the area, where, according to local residents, farmers frequently find bombs and bullets.
An estimated 800,000 tonnes out of the 7.8 million tonnes of explosives dropped by US forces on Vietnam failed to detonate, affecting over 20% of the country.
Quang Tri is the most heavily contaminated province. More than three decades after the war, it is still affected by explosive remnants of war (ERW) which have killed and injured 7,081 people since 1975.